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-13.p
{ Introduction to the Pascal Programming Language
  Dr. Thomas W. MacFarland
  intro_pencil-13.p       
}

{ The purpose of this program is to:

  1.  Demonstrate the structure of a repeat/until loop.

  2.  Demonstrate a counter variable that increments in
      value with each iteration.

  3.  Demonstrate a counter variable that decrements in
      value with each iteration.
}

program Demonstrate_a_Repeat_Until_Loop;

var A, B : integer;

begin

  A := 5;
  repeat
    write('  A = ', A :4);
    A := A + 3;
  until A >= 15; writeln;

  B := 9;
  repeat
    write('  B = ', B :4);
    B := B - 2;
  until B <= -2; writeln;

end.  { intro_pencil-13.p      } 
% pc PASCAL/intro_pencil-13.p
% a.out
  A =    5  A =    8  A =   11  A =   14
  B =    9  B =    7  B =    5  B =    3  B =    1  B =   -1

Please send comments or suggestions to Dr. Thomas W. MacFarland