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-09.p
{ Advanced Pascal Programming Language Exercises
  Dr. Thomas W. MacFarland
  advanced_pencil-09.p
}

{ The purpose of this program is to:

  1.  Demonstrate the use of recursion to produce highly
      compact code.
}

program Demonstrate_Recursion_2;

var Tally : real;

procedure Do_Something_Again(Z : real);
begin
   Z := Z * 2.50;
   writeln('Z      = ',Z    :9:4);
   if Z <= 100 then   
      Do_Something_Again(Z);
   writeln('Z      = ',Z:9:4);
end; {end procedure Do_Something_Again}

begin  (* main program *)
   Tally := 1.5;
   writeln('Tally  = ',Tally:9:4);  
   writeln('******************');
   Do_Something_Again(Tally);
end.  {advanced_pencil-09.p}
%  pc PASCAL/advanced_pencil-09.p
%  a.out
Tally  =    1.5000
******************
Z      =    3.7500
Z      =    9.3750
Z      =   23.4375
Z      =   58.5938
Z      =  146.4844
Z      =  146.4844
Z      =   58.5938
Z      =   23.4375
Z      =    9.3750
Z      =    3.7500

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