Constants in Pascal

Constants are values that cannot be changed during the execution of a program. Below is an example of how to define and use constants in Pascal.

program Constants;

uses
  SysUtils, Math;

const
  s: string = 'constant';
  n: Integer = 500000000;

var
  d: Double;

begin
  Writeln(s);

  d := 3e20 / n;
  Writeln(d);
  Writeln(Int64(d));

  Writeln(Sin(n));
end.

To run this Pascal program, save the code in a file with a .pas extension (e.g., constants.pas) and then use a Pascal compiler, such as Free Pascal Compiler (FPC) or Delphi, to compile and run the program.

Here is how you can compile and execute it using Free Pascal Compiler:

$ fpc constants.pas
$ ./constants

Expected output:

constant
6.0E+11
600000000000
-0.284704073237544

Now that we understand how to declare and use constants in Pascal, let’s continue learning more about the language.