Advanced Pascal Programming Language Problems

© 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/advanced_pencil-01.p
{ Advanced Pascal Programming Language Exercises
  Dr. Thomas W. MacFarland
  advanced_pencil-01.p
}

{ The purpose of this program is to:

  1.  Demonstrate simple procedures that merely write a
      message to the screen.

  2.  Demonstrate how a procedure can use a non-local variable 
      (i.e., a global variable that is available to all 
      procedures).
}

program Demonstrate_a_Simple_Procedure_Call;

var  Count  : integer;   {Global variable}

{-------------------------------------------------------------------}
procedure Write_a_Message;
begin
   writeln('Here is the message:  Hello.');
end; {procedure Write_a_Message}
{-------------------------------------------------------------------}

{-------------------------------------------------------------------}
procedure Put_in_a_Count_1;
begin
   writeln('And the count is:  ',Count:4);
end; {procedure Put_in_a_Count_1}
{-------------------------------------------------------------------}

{-------------------------------------------------------------------}
procedure Put_in_a_Count_2;
begin
   writeln('And the count is:  ',Count:4);
end; {procedure Put_in_a_Count_2}
{-------------------------------------------------------------------}

{-------------------------------------------------------------------}
procedure Write_the_End;  
begin
   writeln('And you are now at the end.');
end; {procedure Write_the_End}
{-------------------------------------------------------------------}

{-------------------------------------------------------------------}
begin  (* main program *)
   Write_a_Message;
   Count := 1;
     for Count := Count to 4 do
       Put_in_a_Count_1; 
   Count := 2;
     for Count := Count to 6 do
       Put_in_a_Count_2; 
   Write_the_End;   
end.  { advanced_pencil-01.p}
{-------------------------------------------------------------------}
%  pc PASCAL/advanced_pencil-01.p
%  a.out
Here is the message:  Hello.
And the count is:     1
And the count is:     2
And the count is:     3
And the count is:     4
And the count is:     2
And the count is:     3
And the count is:     4
And the count is:     5
And the count is:     6
And you are now at the end.

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