DO-CALC

Timensa Software

Products: DO-CALC

Date: 1983

Type: Cassette

Platform(s): TS 1000

DO-CALC is a multi-function scientific and business calculator program written in BASIC, offering six main modules: a general expression evaluator, N-factorial computation, accounting/statistics, running balance, transformation/regression analysis, and compound interest calculation. The program makes extensive use of numeric constants encoded as variables initialised via PI and EXP arithmetic at startup (lines 4–57), avoiding literal numbers throughout the code to save token space. Memory registers M() and C() with string annotation arrays A$() and B$() provide a ten-slot scratchpad accessible across modules. A printer-aware design threads optional LPRINT and COPY calls throughout every module, and a flicker-prompt subroutine at line 9906 animates the status line by repeatedly printing and clearing a string. The GOTO arithmetic idiom—computing branch targets by summing Boolean expressions multiplied by line numbers—appears frequently as a compact alternative to IF/THEN chains.

Program Analysis

Program Structure

DO-CALC is organised as a menu-driven shell with six independently re-entrant modules. Initialisation (lines 3–79) runs once; the main menu loop lives at line 200; and each module occupies a distinct line-number block chosen so that VAL X$*CT (where CT=1400) jumps directly to the correct module entry point when the user enters a digit 1–7.

Line range	Module
1400–1815	Calculator / expression evaluator
1816–1898	Recall / register display
1900–2662	Clear / exchange register management
2800–2936	N-Factorial
4200–5520	Accounting / Statistics
5600–6995	Running Balance
7000–8362	Transformation / Regression
8400–8610	Compound Interest
9000–9085	Continuation dispatcher
9500–9999	Shared utility subroutines

Constant Initialisation via PI Arithmetic

Lines 4–57 construct every numeric constant used in the program from PI, avoiding literal integers. A=PI/PI gives 1; subsequent additions build 2–10 and composite values like LN=T+A (21, the bottom display line). This shrinks each stored number to a short token sequence and is a well-known ZX81/TS1000 memory optimisation.

Z=0, A=1, B=2, C=3, D=4, E=5, F=6, G=7, H=8, I=9, J=10
T=20, U=30, LN=21 (note: LN shadows the built-in LN function — see Anomalies)
NU4=LN J = ln(10) ≈ 2.3026; LG4=EXP A/J = e^0.1 ≈ 1.1052 (log conversion constants, unused in the visible listing)
FU4=PI/180; DG4=A/FU4 — degree↔radian factors

GOTO Arithmetic Idiom

Throughout the program, conditional branches are collapsed into a single GOTO by summing Boolean-times-line-number products. On the ZX81/TS1000, a false condition evaluates to 0, so only the true term contributes to the target address.

Example at line 1425:

GOTO (1702 AND L$="M")+(1487 AND L$="P" AND TP AND L)+(1600 AND L$="A")+(DS AND L$="Q")+(RC AND L$="R")+(CL AND L$="C")+(CT AND L$="*")+(CT AND L$="-")

This replaces seven separate IF/THEN lines with one, saving significant RAM.

Shared Utility Subroutines

Several high-line-number routines serve multiple modules:

PT (9906) — animated prompt: prints S$ at AT LN,PP with a flicker effect using a blank DIM T$(LEN S$). The FOR W=A TO A loop at 9908 executes exactly once — the loop is just a structured way to run the body; there is no actual iteration.
XS (9900) — Y/N input filter: loops until the user enters exactly “Y” or “N”.
LP (9942) — conditional LPRINT with scroll, used for printer output in statistics and balance modules.
5300 — statistics accumulator reset (TO, NU, SX2).
8350 — regression accumulator reset (CX, CY, CX2, CY2, CXY, NM).

Memory Registers

Ten memory (M) and ten constant (C) registers are provided, each with a 12-character string annotation stored in parallel arrays A$(J) and B$(J). A third array D(J) is used during the Exchange function (line 2500) as a temporary swap buffer for C() values, with C$(J,J+B) used for annotation exchange.

Printer Support

The flag variable TP (0 or 1) gates all LPRINT and COPY calls throughout the program. It is set at line 196/198 by a Y/N prompt at startup. Every module checks TP before sending output, making the printer entirely optional.

Continuation / Re-entry

Flags T1, T2, T3 record whether the accounting, balance, and regression modules have been entered before. The Disposition menu (line 9800) offers a “Continuation” option that routes to line 9000, which inspects these flags and re-enters the appropriate module mid-session, preserving accumulators.

Running Balance Negative Indicator

When the running balance BA goes to zero or below, subroutine 6975 converts each character of the string representation to its inverse-video equivalent by adding 128 to its character code (CODE Y$(P)+128). This gives a visual warning directly in the printed balance without any separate flag or branch.

Regression Module

The regression module (lines 7000–8362) supports linear regression of transformed variables. The user supplies BASIC expressions D$ for F(X) and E$ for G(Y); the program evaluates them with VAL D$ and VAL E$ after setting X and Y. Slope, intercept, standard error, and R² are computed at line 7370–7415 using standard single-pass formulae. A delete mode (DE=-A) allows data points to be removed by subtracting from the accumulators.

Error-Recovery String

The string G$ (line 33) holds an inverse-video message ending with “GOTO ” and is concatenated with a line-number string wherever a recovery instruction is displayed on screen — for example G$+"%1%4%0%0" at line 1813 and G$+"%4%2%9%1" at line 5515. This lets the user manually re-enter a module after an error without restarting the program.

Anomalies and Notable Points

LN variable shadows built-in: The variable LN (set to 21 at line 54) redefines the natural-logarithm keyword for the rest of the program. Any attempt to use the built-in LN function after line 54 would call the variable instead. The program avoids this conflict by storing LN J in NU4 during initialisation (line 28), before LN is overwritten.
FOR W=A TO A at line 9908: The loop iterates exactly once. This is used purely for structural symmetry, not for repetition.
Line 260 range check: CODE X$<T+I OR CODE X$>U+E checks that the entered character is in the range ‘1’–’7′ (codes 29–35 in ZX81 character set), restricting menu input to valid module numbers.
Line 6960: IF CODE Y$=(LN AND NOT TD) uses the variable LN (21, the newline/enter key code) as the test for an ENTER keypress, which is a neat dual use of the renamed variable.
Line 9020 referenced but not defined: Lines 9060, 9070, and 9080 branch to line 9020 when a continuation flag is not set, but line 9020 does not exist in the listing. This causes a “line not found” error and is likely a latent bug — the intent was probably to branch to the menu at MN (200).

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Source Code
FAST 
LET Z=PI-PI
LET A=PI/PI
LET B=A+A
LET C=B+A
LET D=C+A
LET E=D+A
LET F=E+A
LET G=F+A
LET H=G+A
LET I=H+A
LET J=I+A
LET T=J+J
LET U=T+J
LET RX=Z
LET LINK=Z
LET CT=1400
LET L=Z
LET RY=Z
LET NU4=LN J
LET LG4=EXP A/J
LET MN=200
LET FU4=PI/180
LET DG4=A/FU4
LET G$="%T%O% %R%E%C%O%V%E%R% %F%R%O%M% %E%S%T%O%P%-%>%G%O%T%O% "
LET N=Z
LET K=Z
LET KD=Z
LET OL=Z
LET RC=1816
LET CL=1900
LET BK=CT
LET U$="================================"
LET PT=9906
LET XS=9900
LET LP=9942
LET XY=7160
LET AS=4291
LET N$="%O%P%T%I%O%N"
LET M$="%E%N%T%E%R"
LET DS=9800
LET LN=T+A
LET T1=Z
LET T2=Z
LET T3=Z
DIM C$(J,J+B)
DIM A$(J,J+B)
DIM B$(J,J+B)
DIM C(J)
DIM D(J)
DIM M(J)
DIM Q$(J+B)
CLS 
SLOW 
GOSUB 170
LET S$=": PRESS ENTER :"
LET PP=J+D
GOSUB PT
LET PP=Z
PAUSE 4E4
GOSUB 190
IF T1 OR T2 OR T3 THEN GOTO DS
GOSUB MN
PRINT AT A,J+A;".................."
PRINT AT B,J+A;": DO-CALC :";AT C,J+A;"''''''''''''''''''";AT E,Z;"COPYRIGHT 1983 BERNARD V. GERBER"
PRINT AT G,D;"% % %   % % %   % % %   % % %   % % % ";AT H,D;"% %1%   % %2%   % %3%   % %4%   % %5% ";AT I,D;"% % %   % % %   % % %   % % %   % % % ";
PRINT AT J+B,D;"% % %   % % %   % % %   % % %   % % % ";AT J+C,D;"% %6%   % %7%   % %8%   % %9%   % %0% ";AT J+D,D;"% % %   % % %   % % %   % % %   % % % "
PRINT AT J+G,D;"% % %   % % %   % % %   % % %   % % % ";AT J+H,D;"% %.%   % %+%   % %-%   % %*%   % %/% ";AT J+I,D;"% % %   % % %   % % %   % % %   % % % "
RETURN 
CLS 
LET S$="%P%R%I%N%T%E%R% %O%N% %L%I%N%E%? Y/N"
GOSUB PT
GOSUB XS
IF X$="Y" THEN LET TP=A
IF X$="N" THEN LET TP=Z
RETURN 
FAST 
CLS 
PRINT AT C,J+A;"%M%E%N%U";AT E,E;;"1.CALCULATOR",TAB E;"2.N-FACTORIAL",TAB E;"3.ACCOUNTING/STATISTICS",TAB E;"4.RUNNING BALANCE",TAB E;"5.TRANSFORMATION/",TAB H;"REGRESSION",TAB E;"6.COMPOUND INTEREST",TAB E;"7.DISPOSITION"
LET S$=M$+"% "+N$
GOSUB PT
INPUT X$
IF (X$="" OR LEN X$>A OR CODE X$<T+I OR CODE X$>U+E) THEN GOTO 255
CLS 
GOTO VAL X$*CT
CLS 
SLOW 
LET BK=CT
GOSUB 1800
PRINT AT F,Z;"LINK=";LINK
PRINT AT H,Z;"%E%V%A%L%U%A%T%E%:"
LET S$=M$+"% %C%A%L%C%U%L%A%T%I%O%N"
GOSUB PT
INPUT L$
IF L$="" THEN GOTO 1415
PRINT AT LN,Z;"                 "
IF L$<>"M" AND L$<>"P" AND L$<>"A" AND L$<>"Q" AND L$<>"R" AND L$<>"C" AND L$<>"*" AND L$<>"-" THEN GOTO 1430
IF L$="-" THEN IF RX=A THEN LET RX=Z
IF L$="*" THEN IF RX=Z THEN LET RX=A
IF L$="P" AND NOT TP THEN GOTO CT
IF L$="P" AND NOT L THEN GOTO CT
GOTO (1702 AND L$="M")+(1487 AND L$="P" AND TP AND L)+(1600 AND L$="A")+(DS AND L$="Q")+(RC AND L$="R")+(CL AND L$="C")+(CT AND L$="*")+(CT AND L$="-")
GOSUB 1800
PRINT AT F,Z;"LINK=";LINK
LET Y$=L$
LET L=VAL Y$
LET OL=LINK
LET LINK=L
PRINT AT F,Z;"LINK=";OL;AT H,Z;"%E%V%A%L%U%A%T%E";AT J,Z;Y$;AT J+D,Z;"%E%Q%U%A%L%S",,,,L;AT J+H,Z;"%W%H%I%C%H% %I%S% %T%H%E% %N%E%W% >LINK"
GOTO 1411
FAST 
PRINT AT LN,Z;U$
COPY 
IF RX THEN GOTO 1555
GOTO 1415
LET RY=A
GOTO RC
LET N=N+A
IF N=J+A THEN GOTO 1662
LET M(N)=L
CLS 
PRINT AT LN,Z;"M(";N;")=";L
LET S$="%R%E%M%A%R%K%:"
LET PP=T
GOSUB PT
LET PP=Z
INPUT A$(N)
PRINT AT LN,J+F;A$(N)
PAUSE U+T
GOTO RC
CLS 
PRINT AT J,J+B;"N0 SPACE"
PAUSE U+T
GOTO RC
LET K=K+A
IF K<J+A THEN GOTO 1715
GOTO 1662
CLS 
PRINT AT J,Z;"-->INPUT ANY NUMBER/EXPRESSION  TO BECOME C(";K;")";" FOR FORMULA USE";AT Z,Z;G$+"%1%7%1%5"
INPUT K$
LET C(K)=VAL K$
LET P$=STR$ C(K)
PRINT AT LN,Z;"C(";K;")=";C(K)
LET S$="%R%E%M%A%R%K%:"
LET PP=T
GOSUB PT
LET PP=Z
INPUT B$(K)
PRINT AT LN,T;B$(K)
PAUSE U+T
LET S$="%A%G%A%I%N%? Y/N                      "
GOSUB PT
GOSUB XS
IF X$="Y" THEN GOTO 1705
GOTO RC
CLS 
PRINT AT Z,Z;" %Q=QUIT %P=PRINT  %A=ASSIGN M(N)  %M=MAKE C(K)    %R=RECALL %C=CLEAR"
IF TP THEN IF RX THEN PRINT AT B,Z;"(-)=PRINT-RECALL %*=PRINT+RECALL"
IF TP THEN IF NOT RX THEN PRINT AT B,Z;" %-=PRINT-RECALL (*)=PRINT+RECALL"
PRINT AT C,Z;G$+"%1%4%0%0"
RETURN 
CLS 
FAST 
PRINT "%R%E%C%A%L%L";TAB T;"%R%E%M%A%R%K%S"
FOR P=A TO J
PRINT "M(";P;")=";M(P);TAB T;A$(P)
NEXT P
FOR P=A TO J
PRINT "C(";P;")=";C(P);TAB T;B$(P)
NEXT P
IF RY THEN GOTO 1892
PRINT AT LN,Z;"%P=PRINT %C=CLEAR %D=DISP %B=BACK"
INPUT X$
IF X$="P" AND NOT TP THEN GOTO 1873
IF X$="P" AND TP THEN GOTO 1892
IF X$<>"C" AND X$<>"P" AND X$<>"D" AND X$<>"B" THEN GOTO 1873
GOTO (DS AND X$="D")+(BK AND X$="B")+(CL AND X$="C")
PRINT AT LN,Z;U$
IF TP THEN LPRINT 
IF TP THEN COPY 
LET RY=Z
GOTO RC
CLS 
FAST 
PRINT AT E,J+A;N$,,TAB A;"1.CLEAR MEMORY REGISTER(S)",TAB A;"2.CLEAR CONSTANT REGISTER(S)",TAB A;"3.EXCHANGE",TAB A;"4.RECALL(OTHER GOTO""S)"
LET S$=M$+"% "+N$
GOSUB PT
INPUT X$
IF X$<>"1" AND X$<>"2" AND X$<>"3" AND X$<>"4" THEN GOTO 1930
GOTO (1950 AND X$="1")+(2000 AND X$="2")+(1942 AND X$="3")+(RC AND X$="4")
GOSUB 2500
GOTO RC
LET MC=Z
LET REG=N
GOTO 2050
LET MC=A
LET REG=K
GOTO 2050
GOSUB 2400
INPUT X$
IF X$<>"A" AND X$<>"B" AND X$<>"C" THEN GOTO 2052
GOTO (2058 AND X$="A")+(2076 AND X$="B")+(2100 AND X$="C")
CLS 
FOR P=A TO J
IF MC THEN GOTO 2068
LET M(P)=Z
LET A$(P)="            "
LET C(P)=Z
LET B$(P)="            "
NEXT P
IF NOT MC THEN LET N=Z
IF MC THEN LET K=Z
GOTO RC
GOSUB 2130
IF VAL Y$=J THEN GOTO 2058
CLS 
FOR P=A TO (J-VAL Y$)
IF MC THEN GOTO 2093
LET M(P)=M(P+VAL Y$)
LET A$(P)=A$(P+VAL Y$)
LET C(P)=C(P+VAL Y$)
LET B$(P)=B$(P+VAL Y$)
NEXT P
IF NOT MC THEN LET N=N-VAL Y$
IF MC THEN LET K=K-VAL Y$
GOTO RC
GOSUB 2130
IF VAL Y$=J THEN GOTO 2058
CLS 
IF NOT MC THEN FOR P=N TO N-VAL Y$+A STEP -A
IF MC THEN FOR P=K TO K-VAL Y$+A STEP -A
IF MC THEN GOTO 2114
LET M(P)=Z
LET A$(P)="            "
LET C(P)=Z
LET B$(P)="            "
NEXT P
IF NOT MC THEN LET N=N-VAL Y$
IF MC THEN LET K=K-VAL Y$
GOTO RC
CLS 
IF NOT REG THEN GOTO RC
LET S$=M$+"% %N%U%M%B%E%R% %O%F% %R%E%G%I%S%T%E%R%S"
GOSUB PT
INPUT Y$
IF Y$="" THEN GOTO 2140
IF VAL Y$<A OR VAL Y$>J OR VAL Y$>REG THEN GOTO 2140
RETURN 
CLS 
PRINT AT E,J+A;N$;TAB F;"A. ALL REGISTERS",TAB F;"B. UPPER BLOCK",TAB F;"C. LOWER BLOCK"
LET S$=M$+"% "+N$
GOSUB PT
RETURN 
CLS 
FAST 
FOR P=A TO J
LET DR=D(P)
LET D(P)=C(P)
LET C(P)=DR
LET S$=C$(P)
LET C$(P)=B$(P)
LET B$(P)=S$
NEXT P
PRINT AT J,J+C;"%D%O%N%E"
PAUSE U+T
CLS 
RETURN 
CLS 
LET BK=2800
PRINT AT Z,Z;G$+"%2%8%0%0"
LET S$=M$+" N"
GOSUB PT
INPUT Y$
FAST 
IF Y$="" THEN GOTO 2860
CLS 
LET P=INT VAL Y$
IF P<A OR P>U+C THEN GOTO 2800
FAST 
LET NF=A
FOR R=A TO P
LET NF=NF*R
NEXT R
CLS 
PRINT AT Z,Z;U$;AT J,A;"%N%F=";P;" FACTORIAL=";NF;AT LN,Z;"%H%I%T% "+M$
PAUSE 4E4
PRINT AT LN,Z;U$
IF TP THEN COPY 
GOTO 9960
FAST 
LET T1=Z
LET H$=";"
IF T1=A AND TP AND H$<>";" THEN LPRINT U$;TAB J;"CONTINUATION",,,H$
IF NOT T1 THEN GOSUB 5300
LET R1=Z
IF NOT TP THEN GOTO 4214
GOSUB 5400
LET H$=X$
LPRINT 
LPRINT "% %D%A%T%A% % % % % % % % % % % % %R%E%M%A%R%K%S% % % % % % % % "
LET DE=A
LET BK=AS-A
LET T1=A
CLS 
FAST 
GOSUB 5500
PRINT AT LN,Z;"X=?                             " 
INPUT Y$
IF Y$="" THEN GOTO AS+C
IF Y$<>"X" AND Y$<>"S" AND Y$<>"T" AND Y$<>"Q" AND Y$<>"*" AND Y$<>"-" THEN GOTO 4301
IF Y$="T" THEN LET AC=Z
IF Y$="S" THEN LET AC=A
GOTO (DS AND Y$="Q")+(4322 AND Y$="S")+(4322 AND Y$="T")+(4390 AND Y$="*")+(4390 AND Y$="-")+(4500 AND Y$="X")
PRINT AT LN,Z;"  "+Y$;
LET X=VAL Y$
GOSUB 4600
IF R1 THEN IF TP THEN LPRINT Y$;
IF NOT R1 THEN GOSUB XS+U
IF R1 THEN GOSUB PT+J
GOTO AS+A
IF NOT NU THEN GOTO AS-A
LET AV=TO/NU
LET SD=SQR ABS ((SX2-((TO*TO)/NU))/(NU-A))
LET V$="%N%U "
PRINT AT LN,Z;V$;NU
LET Z$=STR$ NU
GOSUB LP
LET V$="%T%O "
PRINT AT T+A,Z;V$;TO
LET Z$=STR$ TO
GOSUB LP
IF AC THEN GOTO 4355
LET S$="%R%E%S%U%M%E%? Y/N"
GOSUB PT
GOSUB XS
IF X$="Y" THEN GOTO AS
IF TP THEN LPRINT U$
FAST 
GOTO 9960
LET V$="%A%V "
PRINT AT T+A,Z;V$;AV
LET Z$=STR$ AV
GOSUB LP
LET V$="%S%D "
PRINT AT T+A,Z;V$;SD
LET Z$=STR$ SD
GOSUB LP
LET S$="%R%E%S%U%M%E%? Y/N"
GOSUB PT
GOSUB XS
IF X$="Y" THEN GOTO AS
IF TP THEN LPRINT U$
GOTO 9960
IF Y$="*" THEN LET R1=A
IF Y$="-" THEN LET R1=Z
GOTO AS
IF NOT NU THEN GOTO AS-A
LET DE=-A
LET S$="%X=?"
GOSUB PT
INPUT X$
IF X$="" THEN GOTO 4510
LET X=VAL X$
LET P$=STR$ X
GOSUB 4600
LET DE=A
PRINT AT LN,Z;"%D%E";X
IF TP THEN LPRINT "%D%E";P$
SCROLL 
GOTO AS
LET TO=TO+DE*X
LET NU=NU+DE*A
LET X2=X*X
LET SX2=SX2+DE*X2
RETURN 
LET TO=Z
LET NU=Z
LET SX2=Z
RETURN 
CLS 
FAST 
LET S$="%E%N%T%E%R% %N%E%W% %H%E%A%D%I%N%G"
GOSUB PT
INPUT X$
IF X$="" THEN LET X$="**"
CLS 
LPRINT U$;TAB J;"NEW HEADING",,,X$,TAB J+F,U$
FAST 
RETURN 
PRINT AT Z,Z;"  %T=TOTALS %S=STATISTICS %Q=QUIT  "
IF R1 THEN PRINT AT A,Z;"%X=DELETE %*=+REMARKS (-)=-REMARKS"
IF R1=Z THEN PRINT AT A,Z;"%X=DELETE (*)=+REMARKS %-=-REMARKS"
PRINT AT B,Z;G$+"%4%2%9%1"
RETURN 
LET T2=Z
LET I$=";"
LET BK=9992
IF T2 AND TP AND I$<>";" THEN LPRINT U$;TAB J;"CONTINUATION",,,I$
IF NOT TP THEN GOTO 5625
GOSUB 5400
LET I$=X$
LPRINT U$,,
LET R1=Z
CLS 
GOSUB 6900
IF T2 THEN GOTO 5737
LET S$=M$+"% %I%N%I%T%I%A%L% %B%A%L%A%N%C%E"
LET TD=Z
GOSUB PT
GOTO 6930
IF Y$="*" OR Y$="-" THEN GOTO 5630
CLS 
GOSUB 6900
LET BA=VAL Y$
LET V$="%B%A$"
PRINT AT LN,Z;V$;Y$
LET Z$=Y$
GOSUB LP-F
GOSUB 6900
LET V$="-$="
PRINT AT LN,Z;V$;
LET TD=A
GOTO 6930
IF Y$="*" OR Y$="-" THEN GOTO 5700
IF CODE Y$<T+C OR CODE Y$>U+I THEN LET TD=B
IF CODE Y$<T+C OR CODE Y$>U+I THEN GOTO 6930
LET EN=VAL Y$
LET V$="-$"
PRINT AT LN,Z;V$;EN;
IF R1 THEN LPRINT V$;Y$;
LET Z$=Y$
IF NOT R1 THEN GOSUB LP-F
IF R1 THEN GOSUB PT+J
LET BA=BA-EN
LET Y$=STR$ BA
IF BA<=0 THEN GOSUB 6975
LET T2=A
GOTO 5680
LET V$="%+$"
PRINT AT LN,Z;V$;Y$(B TO LEN Y$)
LET Z$=Y$(B TO LEN Y$)
GOSUB LP
LET BA=BA+VAL Y$(B TO LEN Y$)
LET Y$=STR$ BA
IF BA<=0 THEN GOSUB 6975
GOTO 5680
FAST 
IF NOT R1 THEN PRINT AT Z,Z;" %Q=QUIT (*)=+REMARKS %-=-REMARKS "
IF R1 THEN PRINT AT Z,Z;" %Q=QUIT %*=+REMARKS (-)=-REMARKS "
PRINT AT A,Z;"   PRECEDE DEPOSITS WITH ""+""    "
PRINT AT B,Z;" DELETE ERROR BY DEPOSITING BACK"
PRINT AT B,Z;G$+"%5%6%0%0"
RETURN 
INPUT Y$
FAST 
IF Y$="" THEN GOTO 6930
IF Y$="Q" THEN LET BK=9992
IF Y$="Q" THEN GOTO 9960
IF Y$="*" THEN LET R1=A
IF Y$="-" THEN LET R1=Z
IF CODE Y$=(LN AND NOT TD) THEN GOTO 5630
IF CODE Y$=(LN AND TD) THEN GOTO 5750
IF NOT TD THEN GOTO 5662
IF TD=A THEN GOTO 5712
IF TD=B THEN GOTO 5714
LET Y$=STR$ BA
FOR P=A TO LEN Y$
LET Y$(P)=CHR$ (CODE Y$(P)+128)
NEXT P
RETURN 
FAST 
LET T3=Z
LET J$=";"
LET SC=8300
DIM R$(U+B)
DIM W$(U+B)
IF T3 AND TP AND J$<>";" THEN LPRINT U$;TAB J;"CONTINUATION",,,J$
LET TZ=Z
GOSUB SC
LET P$=X$
CLS 
IF TP THEN GOSUB 5400
IF TP THEN LET J$=X$
IF T3 THEN GOTO 7420
CLS 
LET S$="%T%R%A%N%S%F%O%R%M% %O%N%L%Y%? Y/N"
GOSUB PT
GOSUB XS
FAST 
IF X$="Y" THEN LET TT=Z
IF X$="N" THEN LET TT=A
IF NOT TT THEN GOTO 7045
GOSUB 8350
LET DE=A
LET TV=A
LET BK=9995
GOTO 7075
LET S$="%T%W%O% %V%A%R%I%A%B%L%E%S%? Y/N  "
GOSUB PT
GOSUB XS
CLS 
IF X$="N" THEN LET TV=Z
IF X$="Y" THEN LET TV=A
LET TZ=A
GOSUB SC
LET S$=M$+"% %F%U%N%C%T%I%O%N% %F%(%X%)"
GOSUB PT
INPUT D$
CLS 
LET X=J
LET W=VAL D$
LET R$="%F="+D$
IF TP THEN LPRINT U$,,R$
IF (TT OR TV) THEN GOTO 7120
IF TP THEN LPRINT 
IF TP THEN LPRINT P$
GOTO XY
LET TZ=B
GOSUB SC
LET S$=M$+"% %F%U%N%C%T%I%O%N% %G%(%Y%)"
GOSUB PT
INPUT E$
CLS 
LET Y=J
LET W=VAL E$
LET W$="%G="+E$
IF TP THEN LPRINT W$,,P$
IF NOT TV THEN LET TZ=C
IF TV THEN LET TZ=D
IF TT THEN LET TZ=E
LET BK=9995
GOSUB SC
PRINT AT T,Z;"X=?                "
INPUT K$
IF K$="" THEN GOTO XY+T
IF K$="Q" THEN GOTO DS
IF TT THEN IF K$="X" THEN GOTO 8200
IF TT THEN IF K$="C" THEN GOTO 7370
LET X=VAL K$
LET TX=VAL D$
LET V$=STR$ TX
IF LN=T+A THEN PRINT AT T,Z;"X=";X;AT T,J+H;TX
IF LN=T THEN PRINT AT T,Z;"%D%X";X;TAB J+H;"% ";TX
IF TP AND LN=T+A THEN LPRINT K$;TAB J+H;V$
IF TP AND LN=T THEN LPRINT "%D%X";K$;TAB J+H;"% ";V$
IF NOT TV THEN SCROLL 
IF NOT TV THEN GOTO XY
GOSUB SC
FAST 
IF LN=T+A THEN PRINT AT LN,Z;"Y=?                "
IF LN=T THEN PRINT AT T+A,Z;"%Y=?             "
INPUT L$
IF L$="" OR L$="Q" OR L$="C" OR L$="X" THEN GOTO 7250
LET Y=VAL L$
LET TY=VAL E$
IF TT THEN LET NM=NM+DE*A
LET O$=STR$ TY
IF LN=T+A THEN PRINT AT LN,Z;;"Y=";Y;TAB J+H;TY
IF LN=T THEN PRINT AT T+A,Z;"%D%Y";Y;TAB J+H;"% ";TY
FAST 
SCROLL 
SCROLL 
SCROLL 
IF TP AND LN=T+A THEN LPRINT L$;TAB J+H;O$
IF TP AND LN=T THEN LPRINT "%D%Y";L$;TAB J+H;"% ";O$
IF TP THEN LPRINT 
IF TT THEN GOTO 7330
IF TV THEN GOTO XY
LET CX=CX+DE*TX
LET CY=CY+DE*TY
LET C2=TX*TX
LET D2=TY*TY
LET CX2=CX2+DE*C2
LET CY2=CY2+DE*D2
LET CXY=CXY+DE*(TX*TY)
LET DE=A
LET LN=T+A
GOTO XY
IF (NOT NM OR NM-B<=Z) THEN GOTO XY
CLS 
FAST 
LET NB=CX2-((CX*CX)/NM)
LET NT=CXY-((CX*CY)/NM)
LET SL=NT/NB
LET IN=(CY/NM)-SL*(CX/NM)
LET SP=CY2-((CY*CY)/NM)
LET SE=SQR ABS ((SP-(SL*NT))/(NM-B))
LET R2=((NM*CXY-CX*CY)/SQR ABS ((NM*CX2-(CX*CX))*(NM*CY2-(CY*CY))))**2
CLS 
PRINT AT Z,Z;U$;AT D,G;"%S%L=";SL;TAB G;"%I%N=";IN;TAB G;"%S%E=";SE;TAB G;"%R%2=";R2;AT J+A,Z;"%G= ";SL;" *%F+ ";IN;AT J+D,Z;"WHERE:",,,AT J+F,Z;"%G=";E$;AT J+H,Z;"%F=";D$;AT LN,Z;"%H%I%T% "+M$
LET T3=A
PAUSE 4E4
PRINT AT LN,Z;U$
IF TP THEN COPY 
LET S$="%R%E%S%U%M%E%? Y/N"
GOSUB PT
GOSUB XS
IF X$="N" THEN GOTO 9960
CLS 
GOTO XY
IF NOT NM THEN GOTO XY
LET DE=-A
LET S$="%X=?"
LET LN=T
GOSUB PT
GOTO 7180
FAST 
LET X$="####%D%A%T%A########################%T%R%A%N%S%F%O%R%M##########"
IF TZ=A THEN PRINT AT Z,Z;G$+"%7%0%7%5"
IF TZ=B THEN PRINT AT Z,Z;G$+"%7%1%2%0"
IF TZ=C OR TZ=D THEN PRINT AT Z,Z;"             %Q=QUIT             "
IF TZ=C OR TZ=D OR TZ=E THEN PRINT AT A,Z;G$+"%7%1%6%0"
IF TZ=C THEN PRINT AT B,Z;R$;AT C,Z;X$
IF TZ=D OR TZ=E THEN PRINT AT B,Z;R$;AT C,Z;W$;AT D,Z;X$
IF TZ=E THEN PRINT AT Z,Z;"   %X=DELETE  %C=COMPUTE  %Q=QUIT  "
RETURN 
LET CX=Z
LET CY=Z
LET CX2=Z
LET CY2=Z
LET CXY=Z
LET NM=Z
RETURN 
FAST 
LET TJ=Z
CLS 
LET BK=8400
LET SK=9600
LET BI=9500
GOSUB SK
LET S$=M$+"% %P%R%E%S% %V%A%L"
GOSUB PT
GOSUB BI
IF X$="?" THEN LET TJ=A
IF X$="?" THEN GOTO 8455
LET PV=VAL X$
GOSUB SK
LET S$="%0%/%0% %I%N%T"
GOSUB PT
GOSUB BI
IF X$="?" THEN LET TJ=B
IF X$="?" THEN GOTO 8490
LET IT=VAL X$/100
GOSUB SK
LET S$="%N%U%M% %P%D%S"
GOSUB PT
GOSUB BI
IF X$="?" THEN LET TJ=C
IF X$="?" THEN GOTO 8522
LET PD=INT VAL X$
GOSUB SK
LET S$="%A%M%O%U%N%T"
GOSUB PT
GOSUB BI
IF X$="?" THEN LET TJ=D
IF X$="?" THEN GOTO 8560
LET AM=VAL X$
IF TJ=D THEN LET AM=PV*(A+IT)**PD
IF TJ=A THEN LET PV=AM*(A+IT)**(-PD)
IF TJ=B THEN LET IT=((AM/PV)**(A/PD))-A
IF TJ=C THEN LET PD=(LN AM-LN PV)/(LN (A+IT))
CLS 
PRINT AT Z,Z;U$;AT C,E;"COMPOUND INTEREST";AT G,G;"%P%V=$";PV;TAB G;"%I%T=";IT*100;" %0%/%0";TAB G;"%P%D=";PD;TAB G;"%A%M=$";AM;AT F+TJ,E;"%?>";AT LN,Z;"%H%I%T% "+M$
PAUSE 4E4
PRINT AT LN,Z;U$
IF TP THEN COPY 
GOTO 9960
CLS 
IF NOT T1 THEN IF NOT T2 THEN IF NOT T3 THEN GOTO MN
FAST 
PRINT AT B,J;"%C%O%N%T%I%N%U%A%T%I%O%N";AT D,J+C;N$,,TAB D;"1.ACCOUNTING/STATISTICS",TAB D;"2.RUNNING BALANCE",TAB D;"3.REGRESSION",TAB D;"4.DISPOSITION"
LET S$=M$+"% "+N$
GOSUB PT
INPUT X$
IF X$<>"1" AND X$<>"2" AND X$<>"3" AND X$<>"4" THEN GOTO 9045
FAST 
CLS 
GOTO (9060 AND X$="1")+(9070 AND X$="2")+(9080 AND X$="3")+(9800 AND X$="4")
IF T1<>A THEN GOTO 9020
GOTO 4203
IF T2<>A THEN GOTO 9020
GOTO 5603
IF T3<>A THEN GOTO 9020
GOTO 7006
INPUT X$
IF X$="" THEN GOTO 9500
IF X$="Q" THEN GOTO DS
FAST 
IF TJ AND X$="?" THEN GOTO 9500
RETURN 
CLS 
FAST 
PRINT AT Z,J+B;"%Q=QUIT";AT B,D;M$+"% %?% %F%O%R% %U%N%K%N%O%W%N% %O%N%L%Y";AT D,Z;G$+"%8%4%0%0"
RETURN 
FAST 
CLS 
PRINT AT G,J+A;"%O%P%T%I%O%N%S",,TAB J;"1.MENU",TAB J;"2.RECALL",TAB J;"3.BACK";TAB J;"4.CONTINUATION",TAB J;"5.SAVE ""DO-CALC""",TAB J;"6.STOP"
LET S$=M$+"% "+N$
GOSUB PT
INPUT X$
FAST 
IF X$<>"1" AND X$<>"2" AND X$<>"3" AND X$<>"4" AND X$<>"5" AND X$<>"6" THEN GOTO 9811
GOTO (MN AND X$="1")+(RC AND X$="2")+(BK AND X$="3")+(9000 AND X$="4")+(9832 AND X$="5")+(9818 AND X$="6")
CLS 
PRINT AT H,D;"OPEN FOR DIRECT COMMANDS";TAB I;"(GOTO DS-AFTER)"
STOP 
CLS 
PRINT AT J,J+B;"RECORDER?"
LET S$="%H%I%T% "+M$
GOSUB PT
PAUSE 4E4
SAVE "DO-CALC"
GOTO 150
INPUT X$
IF X$<>"Y" AND X$<>"N" THEN GOTO XS
RETURN 
DIM T$(LEN S$)
SLOW 
FOR W=A TO A
PRINT AT LN,PP;T$;AT LN,PP;S$;AT LN,PP;T$;AT LN,PP;S$
NEXT W
RETURN 
LET S$="%R%E%M%A%R%K%:"
LET PP=T
GOSUB PT
LET PP=Z
INPUT Q$
PRINT AT LN,T;Q$
SCROLL 
IF TP THEN LPRINT AT LN,T;Q$
FAST 
RETURN 
IF TP THEN LPRINT Y$
SCROLL 
RETURN 
IF TP THEN LPRINT V$;Z$
SCROLL 
RETURN 
IF NOT R1 THEN GOSUB LP-F
IF R1 THEN IF TP THEN LPRINT V$;Z$;
IF R1 THEN GOSUB PT+J
GOSUB 5500
RETURN 
LET S$=M$+"% %A%S% %C%O%N%S%T%A%N%T%(%S%)%? Y/N       "
GOSUB PT
GOSUB XS
FAST 
IF X$="N" THEN GOTO DS
CLS 
GOTO 1705
CLS 
GOTO 5737
CLS 
GOTO XY
STOP 

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