TOPS-20 PASCAL Language Manual - Bitsavers

PROGRAM Calculator (INPUT, OUTPUT);
TYPE Yes_No = (Yes, No);
VAR Subtota 1, OpeT'arld ! REAL.;
EGuatior. ! BOOL.EAN;
Ope T'ato T' ! CHAR f
AnsweT' ! Ye!:; .... No ji
INTRODUCTION
Declaration
Section
PROCEDURE InstT'ucticms;
BEe, IN
W Fn TEL N (' T his pro g r a ITI
Procedure
Block
add s, sub t T' act s, lTIul tip 1 i e s, and');
WRITEL.N ('divides real nUlTlbers. Enter a nUlTlber in response');
WRITELN ('to the Operand! prolTlPt and enter an operator -- ');
WRITELN ('tf -, *, /, or = -- in response to the Operator!');
WRITELN ('proITlPt. The progralTl keeps a running subtotal');
WRITELN ('until ~ou enter an e~ual sign (=) in response to');
WRITELN ('the Operator! prolTlPt. You can then exit frolTl');
W F~ I TEl ... N (' t h €-! F' T' 0 ~.;! T' a ITI 0 I' b f::' !:.I ina new s f~ t 0 f cal c 1 •.11 at i C) n!:; • ' ) ;
ENI; (*end of procedure Instructions*)
BEGIN
WRITE ('Do YOU need instructions? r~pe
RFADl..N (An~; we Y') ;
If Answer = Yes THEN Instructions;
yes or no. ');
F~FF'EAT
EC~l..Iat:i.on
!"" FAL~:;F;
Subtota 1 : ::.. 0;
WR I TE (' ClF'e rand! ' ) ;
READLN (Subtotal);
Executable
Section
WHILE (NOT [~uation)
DO
BEGIN
WRITE ('Operator!');
READLN (Operator);
IF (Operator = '=') THEN
BEGIN
E~uation
!= TRUE;
WRITELN ('The answer is ',Subtotal!5!2)
END
ELSE
BEGIN
WRITE ('Operand!');
READLN (Operand);
CASE Operator OF
END;
'+ '
. _. Subtotal +
.-
Operand;
Ope T'and;
Operand;
Operand
Subtotal
'- , Subtotal ' .- Subtotal -
'*' Subtotal
,- Subtotal *
IIi Subtotal .. ,-- Subtotal /
END;
WRITELN ('The subtotal is ',Subtotal!5!2)
END
WRITE ('An~ more calculations? T~pe ~es or no.');
READLN (Answer);
UNTIL Answer = No;
END.
MR·S-3150-83
Figure 1-1:
Structure of a PASCAL Program
1-3