Introduction to the Pascal Programming Language
© 1998 by Dr. Thomas W. MacFarland -- All Rights Reserved
Instructions: Review the following program and see if you can predict the outcome by completing a "pencil trace" of the code. Program output is provided at the end of this page. Compiler: The program was prepared using Standard Pascal on a UNIX-based host computer.
% cat PASCAL/intro_pencil-15.p
{ Introduction to the Pascal Programming Language
Dr. Thomas W. MacFarland
intro_pencil-15.p
}
{ The purpose of this program is to:
1. Demonstrate Boolean math.
2. Demonstrate the : symbol to format the printout of
Boolean true and false output.
}
program Demonstrate_Boolean_Math;
var A, B, C : boolean;
D, E : integer;
begin
D := 0;
E := 1;
A := D = E;
B := D = (E + 1);
C := D < E;
write('A = ',A :6, ' '); write('B = ',B :6, ' ');
write('C = ',C :6, ' '); write('D = ',D :6, ' ');
write('E = ',E :6, ' '); writeln;
A := B and C;
write('A = ',A :6, ' '); write('B = ',B :6, ' ');
write('C = ',C :6, ' '); writeln;
A := B and not C;
write('A = ',A :6, ' '); write('B = ',B :6, ' ');
write('C = ',C :6, ' '); writeln;
A := B or C;
write('A = ',A :6, ' '); write('B = ',B :6, ' ');
write('C = ',C :6, ' '); writeln;
A := (B and C) or not (C);
write('A = ',A :6, ' '); write('B = ',B :6, ' ');
write('C = ',C :6, ' ');
writeln;
end. { intro_pencil-15.p }
% pc PASCAL/intro_pencil-15.p
% a.out
A = false B = false C = true D = 0 E = 1
A = false B = false C = true
A = false B = false C = true
A = true B = false C = true
A = false B = false C = true