Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1)— passes the first character of the control string as a command byte.POKE 16515, VAL P$(2)— passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields fromP$into addresses 16516–16519. - Lines 17–19 copy up to
PEEK 16519characters fromQ$(offset byPEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100"at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation. - Conditional skip on “V” mode: Line 21 checks
P$(1)="V"and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back toQ$. - Null-guard on P$(2): Line 12 replaces a space in
P$(2)with"0"before callingVAL, preventing a runtime error on an empty field. - PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42/ED 52(SBC HL,BC/SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations. CD BB 02— repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F— calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EFbytes —RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yysequences) dispatches on the command byte stored at 0x4082, handling command codes including0x0A,0x08,0x06,0x33,0x38,0x29,0x28, and0x3B.
Address Map
| Address | Role |
|---|---|
0x4000 (16384) | Start of REM machine code block |
0x4082 (16514) | Command byte (from P$(1)) |
0x4083 (16515) | Sub-parameter 1 |
0x4084–0x4087 | Additional parameters from P$(4..10) |
0x4088 (16520) | Data buffer start / return value |
0x4179 (16729) | Machine code entry point (RAND USR target) |
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"B\B9\B9\B9\D3\E8\B9\A7\A7 itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"D
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
\B2\B2\A9\A9\BE\BE
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
A
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
F
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"AE itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"A itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"A
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
E
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
D itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"B itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"C
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"C itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"D\CF\E5E
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
F\E1E\EB\E9A\AF\CBF\CB\CBF\AF\C9
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
\AB\D5\E5\EBE\E1EF\EBE\FEA\AF
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
F\CB\CB\C7\CB
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
B\AF\CBF itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
B\EB\CB\CBF itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
B\CE\C1\E5\E1\C9
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
A\FE\FE itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"B
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
\FE\FE
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
C\FEB
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
\CB
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
\FE
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
A itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"AA\FE
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
E
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
E
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
E itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"\FA\FE
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
CA\FE\FE\C2\F4A
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
AA\FE\D2\F4\FE itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"\DA\F4A\FE\D2\F4\CD itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"DE\CD itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"D\EF\CD\A7
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
EA\FE\D2\F4F
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
\E5AF
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"\F8
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
\A7\ED\E1\D2\F4\EDB
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
C\A9\ABAB\CBFE
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
E
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
\AFA\FE
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
AA\C5E\FE itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
F\F8\C1\CD\B4\CD\F6\CD\CB\E7\AFA\FE\C1\CD\CBF\C0A\D6 itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"\D8
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
A\A9E\D6A\D6 itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"\D8\B2\C3
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
\E5EF
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
\E5\CD itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"DE
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
A\CD itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"D\EF\CD\A7
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
E itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"C
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
D\F2\CDE
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
A\CD itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"D\EF\CD\A7
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
E\E1\A7\ED itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4" itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"C
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
D\F3\F2\CD\E1\C1\A3\C5\E5\BA itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"\D1\CDAD\C8A\AF\CB\D7\AF\CD\C9\FE\D3\CD\CD\C9\CD\C9\D1\CDAD\C8\CB
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
A\AF\CB\D7\AF
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
B\CD\C9\D9\E5
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
A\AB
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
E
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
F\A7\EDA\FE
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
B
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
B\AB\E1\FE\FE itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
A\CD\CD\CD
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
D\CD\F0\FE
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
A\CD
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
D\CD\CD\D1 itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"\CD\C9A\AF\CB\AF
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
A\AB\AD
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
A\A9\AB\CD
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
B
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
F\CD\BB
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
C\FA\CD\BB
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
D\F7\CD\BDE\CB\D0\CD\CB itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"D\CB\A7\AFA\B4\CD\F6
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
A\A9\AB\CD\CB\AF\CBFA\D0\D6A\D0\D0\CD itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"B\ED\AB
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
A\AD\EB\A7\EDFEA\D0
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
\FE\EDB\A9
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
A\AB\A7\ED\EE\CD\CB\CF\CB\DF\AF\D2\CD\ED\AB
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
E\FEA\FE itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"\CCA\AF\CBF\CB\AF\AFE\CB\EF\AFEA\D1\EDB\AB
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
\A9
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
A\A9\A7\ED\F6A\D0\FE\B0A\AF
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
D\CB\AF\AFE\D1\C3
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
\CBF\CA
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
\B4\CD\CD\F6\B2\C3
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
\FE\E3\CD\BB
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
C\FAA\AF\CBF\CD
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
FE\D1\CF
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
C
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
\FEA\FE\FE
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
F\FE
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
A\FE\FE\CD
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
F
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
A\ABA\AF\CBE\D6A\AF\CBF\B0\CD
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
AE
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
\EB\C2\CD\F6\CD
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
B
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
F\CD\BB
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
C\FAA\AF\CBF\CD
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
FE\D1A\FE
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
A\C8\FEA\CD\AB
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
A\A9\CD\C9\C5\D5\F2\ED\AB\CD\E5A\F2\D6 itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"C\CD itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"DE
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
A\CD itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"D\EF\CD\A7
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
EA\F3\D6 itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"CF
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
D\D1\E1\C1\C8\C5\E5\EB\CC\F0A\FE itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4" itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"B\EDB\AB
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
A\AD\A7\ED\C8\D8A\FE
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
\CD
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
B\CB\D7\AF\EB\CD\C9A\FEA\A7\CBA\AF\E0\CB\CF\CB\DF\D5\E5\AF
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
A\AB
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
B\EDB\AD itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"B\ED\AB\CD\E1\D1A\AF\C0\EDB\A9
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
A\AB\A7\ED
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
E itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"C\EDB\A9\ED\AB\C2\C3
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
EA\FE
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
\CB\C1 itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"A\FE itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"C\CB\FE itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
D\FE\FE itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"B\CB\CB\C9 itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56710 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"D\E1
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
A\A9\AB\B0\C3
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
\FE
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
C\FE\EBA\AF\CB\AF\C3A\AF\CBE\C2\C3
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
E
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
\C4\C3
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
A\A9E\FE
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
A\FEE\FE\CD\CB\D7\AF
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
Skip to content
Screen Machine
Machine language sub-routine that allows inputs anywhere on screen, complete error checking, automatic formatting (dates, decimals), and advance directly to next prompt.
Program Analysis
This program implements a data entry routine, using an embedded machine code routine stored in a REM statement at line 1. The machine code begins at address 16384 (0x4000) and is invoked via RAND USR 16729, handling screen and keyboard input operations. The BASIC shell (lines 10–25) acts as a wrapper, using PEEK and POKE at addresses 16514–16520 to pass parameters to and from the machine code, including a string P$ for control parameters and Q$ for data. The routine includes logic for a “V” mode (line 21) that skips writing results back to Q$, suggesting a verify or view-only pass.
Program Structure
The program is organized into two distinct layers. The BASIC shell occupies lines 1–100, while the heavy lifting is performed by Z80 machine code embedded in the REM statement at line 1. Line 9 uses the GO TO VAL "100" idiom to jump past the data and REM metadata to the actual program entry point. Lines 10–29 form a subroutine (returned from at line 29) that acts as the interface between BASIC and the machine code.
REM-Embedded Machine Code
Line 1’s REM statement contains several hundred bytes of Z80 machine code. Because the Spectrum/TS2068 BASIC system stores the REM text starting at a known offset into the program area, the machine code lands at a predictable address in RAM. The entry point is called via RAND USR 16729 at line 20, placing the start of executable code at address 16729 (0x4179) within the block. Line 2 contains a short secondary REM, likely acting as padding or a data table.
Parameter Passing Convention
The BASIC wrapper communicates with the machine code through a set of fixed memory locations POKEd before the RAND USR call:
POKE 16514, CODE P$(1) — passes the first character of the control string as a command byte.POKE 16515, VAL P$(2) — passes a numeric sub-parameter.- Lines 14–16 (
FOR Q=2 TO 5) pack additional two-character numeric fields from P$ into addresses 16516–16519.
- Lines 17–19 copy up to
PEEK 16519 characters from Q$ (offset by PEEK 16518) into addresses starting at 16521, providing the data buffer.
After the machine code returns, lines 22–24 read the (possibly modified) buffer back into Q$, closing the round-trip data exchange.
Notable BASIC Techniques
- VAL for line numbers:
GO TO VAL "100" at line 9 is a memory-saving technique; storing the target as a string constant avoids the five-byte floating-point number representation.
- Conditional skip on “V” mode: Line 21 checks
P$(1)="V" and jumps to line 25, bypassing the write-back loop (lines 22–24). This implements a view/verify mode where the buffer is not flushed back to Q$.
- Null-guard on P$(2): Line 12 replaces a space in
P$(2) with "0" before calling VAL, preventing a runtime error on an empty field.
- PEEK 16520 result read-back: Line 25 (
LET Q=PEEK 16520) retrieves a return value left by the machine code in the data buffer area.
Machine Code Overview
The Z80 code is extensive (over 400 bytes). Key patterns visible in the hex dump include:
- Frequent use of
ED 42 / ED 52 (SBC HL,BC / SBC HL,DE) for 16-bit arithmetic, suggesting cursor position or string length calculations.
CD BB 02 — repeated calls to address 0x02BB, which is the TS2068/Spectrum ROM routine for scanning the keyboard.CD 2B 0F — calls to 0x0F2B, the ROM’s “wait for keypress” or display routine.EF bytes — RST 0x28, the floating-point calculator, used for numeric display formatting.- A jump table near the start of the code (based on the series of
FE xx 28 yy sequences) dispatches on the command byte stored at 0x4082, handling command codes including 0x0A, 0x08, 0x06, 0x33, 0x38, 0x29, 0x28, and 0x3B.
Address Map
Address Role 0x4000 (16384)Start of REM machine code block 0x4082 (16514)Command byte (from P$(1)) 0x4083 (16515)Sub-parameter 1 0x4084–0x4087Additional parameters from P$(4..10) 0x4088 (16520)Data buffer start / return value 0x4179 (16729)Machine code entry point (RAND USR target)
Metadata and Provenance
REM statements at lines 91–96 identify the routine as SCREEN / 2D.02 / 3140, copyright 1983 by Management Services Co. This version/build numbering suggests the machine code was part of a larger commercial library of data entry utilities distributed as BASIC programs with embedded Z80 routines.
Content
Image Gallery
Source Code
1 REM \00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\1B\42\64\43\B9\42\B9\42\B9\42\D3\42\E8\42\03\43\B9\42\46\45\A7\45\46\45\A7\45\1D\46\28\46\46\45\00\88\80\B2\B2\A9\A9\BE\BE\28\34\37\37\2A\28\39\0F\00\10\33\1A\3E\1A\33\1A\29\11\0E\18\0D\1B\1C\00\16\1C\1D\CF\18\E5\21\82\40\7E\16\00\5F\E1\19\5E\23\56\EB\E9\3A\AF\40\CB\8F\CB\97\CB\9F\32\AF\40\C9\06\02\11\AB\40\D5\E5\EB\5E\23\56\E1\7E\4F\EB\7E\FE\76\3A\AF\40\20\0F\CB\47\20\05\CB\C7\23\18\03\CB\87\2B\32\AF\40\71\CB\4F\20\03\23\18\01\2B\EB\CB\57\20\08\CB\5F\20\03\23\18\01\2B\10\CE\C1\E5\60\69\73\23\72\E1\C9\21\82\40\06\00\3A\82\40\FE\38\28\22\FE\33\28\1B\00\00\28\16\FE\29\28\11\FE\28\28\0C\FE\3B\28\07\00\00\00\00\18\08\04\04\04\04\04\04\CB\00\70\78\FE\0A\20\1A\06\03\21\85\40\3A\83\40\FE\03\30\04\0E\17\18\02\0E\18\71\0E\01\23\10\FA\18\10\FE\06\20\0C\3A\87\40\FE\04\28\05\FE\06\C2\F4\40\21\5A\00\22\23\40\22\0A\40\3A\87\40\FE\21\D2\F4\40\FE\01\DA\F4\40\3A\84\40\FE\17\D2\F4\40\CD\1D\15\3E\21\CD\1D\15\EF\04\34\CD\A7\0E\03\3A\85\40\FE\20\D2\F4\40\6F\26\00\09\E5\3A\87\40\4F\06\00\09\01\F8\02\A7\ED\42\E1\D2\F4\40\ED\4B\0C\40\09\22\A9\40\22\AB\40\3A\3B\40\CB\7F\3E\80\20\02\3E\00\32\AF\40\3A\82\40\FE\0A\28\11\3A\87\40\47\C5\21\89\40\7E\FE\01\30\0F\23\10\F8\C1\CD\05\41\21\B4\40\CD\F6\40\18\28\CD\05\41\CB\E7\32\AF\40\21\89\40\3A\82\40\FE\08\28\22\C1\CD\14\41\CB\6F\C0\3A\83\40\D6\01\D8\2A\A9\40\7E\D6\80\77\18\06\3A\83\40\D6\01\D8\21\B2\40\C3\00\41\E5\7E\6F\26\00\E5\CD\1D\15\3E\0A\CD\1D\15\EF\05\24\34\CD\A7\0E\21\1C\00\09\7D\32\F2\40\CD\20\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\E1\A7\ED\42\01\1C\00\09\7D\32\F3\40\21\F2\40\CD\12\41\E1\C1\05\28\A3\C5\23\E5\18\BA\06\01\21\D1\40\CD\14\41\3A\87\40\3D\C8\47\3A\AF\40\CB\D7\32\AF\40\CD\14\41\C9\78\FE\04\21\D3\40\20\09\CD\12\41\23\23\CD\12\41\C9\CD\14\41\C9\21\D1\40\CD\12\41\3A\87\40\3D\C8\47\CB\00\3A\AF\40\CB\D7\32\AF\40\2B\CD\14\41\C9\21\D9\40\E5\2A\AB\40\06\00\0E\0F\A7\ED\42\3A\83\40\FE\03\38\02\2B\2B\22\AB\40\E1\FE\03\30\20\FE\01\20\13\06\0A\CD\14\41\06\03\23\23\CD\14\41\23\23\CD\12\41\18\22\06\0D\CD\14\41\23\23\18\F0\FE\03\20\09\06\0A\CD\14\41\06\07\18\07\06\0D\CD\14\41\06\04\23\23\CD\14\41\21\D1\40\06\01\CD\14\41\C9\3A\AF\40\CB\87\32\AF\40\2A\AB\40\22\AD\40\2A\A9\40\22\AB\40\CD\2B\0F\CD\BB\02\2C\20\FA\CD\BB\02\44\4D\51\14\28\F7\CD\BD\07\7E\CB\77\32\D0\40\20\50\CD\05\41\CB\67\28\1D\CB\A7\32\AF\40\3A\87\40\47\21\B4\40\CD\F6\40\2A\A9\40\22\AB\40\CD\05\41\CB\87\32\AF\40\CB\6F\28\07\3A\D0\40\D6\80\18\03\3A\D0\40\21\D0\40\77\CD\12\41\1B\ED\53\AB\40\2A\AD\40\EB\A7\ED\52\38\9F\3E\7A\32\D0\40\18\02\18\96\FE\77\20\23\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\EE\CD\05\41\CB\CF\CB\DF\32\AF\40\21\D2\40\CD\12\41\13\ED\53\AB\40\18\2E\FE\74\20\60\3A\82\40\FE\01\30\CC\3A\AF\40\CB\6F\28\09\CB\AF\32\AF\40\3E\88\18\07\CB\EF\32\AF\40\3E\8A\32\D1\40\ED\5B\AB\40\12\18\02\18\A9\2A\A9\40\A7\ED\52\38\F6\3A\D0\40\FE\74\21\B0\40\3A\AF\40\28\0D\CB\AF\32\AF\40\3E\88\32\D1\40\C3\00\41\CB\6F\CA\00\41\21\B4\40\CD\05\41\CD\F6\40\21\B2\40\C3\00\41\FE\E3\20\17\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\CF\0C\06\00\FE\7A\28\18\FE\76\28\14\FE\73\28\0F\FE\70\28\0A\FE\71\28\05\FE\72\20\93\04\04\04\04\78\32\88\40\CD\23\0F\2A\AB\40\3A\AF\40\CB\67\28\13\7E\D6\80\77\3A\AF\40\CB\6F\28\12\21\B0\40\CD\00\41\18\0A\3E\00\77\EB\21\C2\40\CD\F6\40\CD\2B\0F\CD\BB\02\2C\20\FA\3A\AF\40\CB\7F\20\03\CD\23\0F\3E\88\32\D1\40\3A\82\40\FE\0A\C8\FE\08\3A\87\40\47\CD\05\41\21\89\40\22\AB\40\2A\A9\40\28\04\CD\14\41\C9\C5\11\89\40\D5\11\F2\40\ED\53\AB\40\CD\12\41\E5\3A\F2\40\D6\1C\CD\1D\15\3E\0A\CD\1D\15\EF\04\34\CD\A7\0E\3A\F3\40\D6\1C\6F\26\00\09\7D\D1\E1\C1\77\05\C8\23\C5\E5\EB\18\CC\11\F0\40\3A\82\40\FE\08\20\01\1B\ED\4B\AB\40\2A\AD\40\A7\ED\42\C8\D8\3A\83\40\FE\02\CD\05\41\28\0B\CB\D7\32\AF\40\45\EB\CD\14\41\C9\3A\82\40\FE\08\3A\87\40\20\03\A7\CB\07\45\90\47\3A\AF\40\28\E0\CB\CF\CB\DF\D5\E5\32\AF\40\2A\AB\40\2B\ED\5B\AD\40\1B\ED\53\AB\40\CD\14\41\E1\D1\3A\AF\40\18\C0\ED\5B\A9\40\2A\AB\40\A7\ED\52\28\02\30\12\3E\1C\ED\5B\A9\40\12\13\ED\53\AB\40\21\C2\40\C3\00\41\45\0E\04\3A\82\40\FE\02\28\02\CB\C1\1A\FE\1C\30\25\CB\41\20\14\FE\01\38\2D\FE\16\28\29\FE\1B\20\08\CB\49\20\04\CB\C9\18\1D\E1\2A\A9\40\22\AB\40\21\B0\40\C3\00\41\FE\76\28\0C\FE\26\30\EB\3A\AF\40\CB\91\32\AF\40\13\10\C3\3A\AF\40\CB\51\20\9E\21\C2\40\C3\00\41\3E\02\32\83\40\21\C4\40\C3\00\41\06\07\2A\A9\40\7E\FE\33\28\0A\FE\3E\28\05\FE\29\20\06\04\04\78\32\88\40\CD\05\41\CB\D7\32\AF\40\06\00\0E\11\A7\ED\42\22\AB\40\06\12\21\F0\40\CD\14\41\C9\24\25\21
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.
People
No people associated with this content.
E\A7\ED\AB\F0\CD\C9
2 REM
9 GOTO VAL "100"
10 REM ** SCREEN **
11 POKE 16514,CODE P$(1)
12 IF P$(2)=" " THEN LET P$(2)="0"
13 POKE 16515,VAL P$(2)
14 FOR Q=2 TO 5
15 POKE 16514+Q,VAL P$(2*Q-1 TO 2*Q)
16 NEXT Q
17 FOR Q=1 TO PEEK 16519
18 POKE 16520+Q,CODE Q$(Q+PEEK 16518-1)
19 NEXT Q
20 RAND USR 16729
21 IF P$(1)="V" THEN GOTO VAL "25"
22 FOR Q=1 TO PEEK 16519
23 LET Q$(Q+PEEK 16518-1)=CHR$ PEEK (Q+16520)
24 NEXT Q
25 LET Q=PEEK 16520
29 RETURN
90 REM DATA ENTRY ROUTINE
91 REM SCREEN / 2D.02 / 3140
95 REM COPYRIGHT (C) 1983 BY:
96 REM MANAGEMENT SERVICES CO.
100 REM ** START PROGRAM HERE
Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.