unit Perims;

(*****************************************************************)

(*                                                               *)

(* This unit contains three procedures to calculate perimieters  *)

(* of three geometric shapes.                                    *)

(*                                                               *)

(*****************************************************************)

interface

   procedure Perimeter_Of_Circle(Radius : real;

                                 var Perimeter : real );

   procedure Perimeter_Of_Square(Length_Of_Side : real;

                                 var Perimeter : real);

   procedure Perimeter_Of_Rectangle(Length,Width : real;

                                    var Perimeter : real);
implementation
var My_Pi : real;
procedure Perimeter_Of_Circle;

begin

   Perimeter := My_Pi * 2.0 * Radius;

end;
procedure Perimeter_Of_Square;

begin

   Perimeter := 4.0 * Length_Of_Side;

end;
procedure Perimeter_Of_Rectangle;

begin

   Perimeter := 2.0 * (Length + Width);

end;
begin                   (* This is the initialization code *)

   My_Pi := 3.14159267;

end.  (* of unit Perimeters *)


Result of execution

(A unit cannot be executed)