Address File

ADDFILE is a ZX81/TS1000 address-book manager published in Compute! magazine (March 1983) that stores up to 100 records, each holding a name, address, city, ZIP code, and phone number across five parallel string arrays. The program offers four operating modes — Entry, Change, List, and Search — selectable from a menu, with Search supporting lookup by either full name or city using exact-string matching against fixed-width string slices. The FAST/SLOW toggle is used during search loops to accelerate scanning. Fixed-length DIM declarations (e.g., 30, 25, 12, 5 characters) require users to pad or truncate input to fit array widths, and substring slice notation is used consistently for both assignment and comparison.

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Program Analysis

Program Structure

The program is divided into clearly separated functional blocks, each starting at a round line number, making the code easy to navigate by section:

Line Range	Function
1–17	REMs and array declarations
25–75	Initialisation and main menu
500–570	CHANGE mode
1000–1150	ENTRY mode
1500–1550	LIST mode
2000–2165	SEARCH mode
5000–5050	Splash screen and initialisation entry point

The program starts at line 5000 via the GOTO 35 on line 35, which is itself reached from the splash screen at line 5030 (GOTO 38). Line 38 does not exist, so execution falls through to line 40, which sets the label variables for each mode. This is a deliberate technique to skip re-initialising those labels on subsequent returns to the menu.

Data Storage

All data is held in five parallel two-dimensional string arrays, each with 100 rows:

• N$(100,30) — name (30 chars)
• A$(100,30) — address (30 chars)
• C$(100,25) — city (25 chars)
• P$(100,12) — phone number (12 chars)
• Z$(100,5) — ZIP code (5 chars)

Two single-row scratch arrays, S$(1,30) and T$(1,30), are used to hold search terms for name and city respectively before comparison. The variable L tracks the index of the last entered record, and N is used as a snapshot of L at menu time to allow the ENTRY loop to begin at the correct position.

Note that DIM L(1) on line 10 declares a numeric array, while the scalar variable L used throughout the program is a completely separate entity — the array L() is never referenced again.

Menu and Mode Dispatch

The main menu (lines 49–75) uses a string INPUT B$ and a chain of IF/GOTO tests to dispatch to the correct mode. The destination line numbers are pre-stored in variables CHANGE, ENTER, LIST, and SEARCH (lines 40–46), but these variables are never actually used in the GOTO statements — the GOTOs on lines 67–70 use the literal values 500, 1000, 1500, and 2000 directly. The label variables serve no functional purpose.

Entry Mode

Entry mode (lines 1000–1150) loops from N+1 to 100 using a FOR/NEXT construct. After each record is entered, the user is prompted with “ANOTHER ENTRY?? (Y/N)”; any response other than “Y” exits via GOTO 47, which snapshots L into N before returning to the menu. If the loop reaches record 100, line 1015 exits early with a “LIST FILLED” message.

Search Mode

Search mode (lines 2000–2165) supports two search types selected by entering “N” or “C”. For city search, T$(1,1 TO 25) holds the target string and is compared slice-by-slice against C$(S,1 TO 25). For name search, S$(1,1 TO 30) is compared against N$(S,1 TO 30). In both cases FAST mode is enabled before the loop to accelerate scanning, and SLOW is restored after.

The city search on a match jumps to line 2160, prints the record, then falls to GOTO 2041 — the NEXT S statement — continuing the loop to find all matching cities. The name search jumps to line 2160 similarly, but after printing also falls to GOTO 2041, so it too will continue scanning for further name matches rather than stopping at the first hit.

List Mode

List mode (lines 1500–1532) uses SCROLL between each printed field to advance the display without clearing the screen, giving a rolling-feed effect. Each record’s index number is printed alongside the name (PRINT N$(V);V) for reference in CHANGE mode.

Change Mode

Change mode (lines 500–570) prompts for a record number C, displays the existing fields, then prompts for corrected values one field at a time. Assignment uses substring slice notation for name, address, and city (e.g. LET N$(C,1 TO 30)=Y$), but for ZIP and phone uses bare array element assignment (INPUT Z$(C), INPUT P$(C)), which is functionally equivalent for single-row-dimension slices.

Notable Techniques and Anomalies

• Line 5030 uses GOTO 38, a non-existent line, to fall through to line 40 — a deliberate idiom to skip lines 35 (the initial GOTO 5000) while landing exactly at the label-variable initialisation block.
• Line 47 (LET N=L) is placed before the CLS at line 49 rather than inside the menu, ensuring N is always updated on each menu visit so ENTRY mode resumes at the correct position.
• The unused DIM L(1) array declaration consumes memory without serving any purpose and may reflect an early draft of the program where a numeric array was planned.
• Lines 2140–2145 (an unreachable block after a city search match) print record fields and pause, but are never reached because all match branches jump to line 2160. This is dead code.
• Line 113 (PRINT) appears in isolation with no apparent purpose; it is never reached by normal program flow and seems to be a remnant of editing.
• PAUSE 30000 is used as an indefinite pause (the user presses a key to continue), which is a standard ZX81 idiom since there is no INKEY$-based wait built in.
• Lines 5035–5050 provide a SAVE routine under a custom filename with an auto-run flag, saving the program as 1000 6 (with the inverse-video character encoding the auto-run marker).