program Calculate_Area_Of_Shapes;

uses Areas,Crt;
var In_Char : char;

    Length,Width,Height,Base,Radius : real;
begin  (* main program *)

   repeat

      Writeln;

      Writeln('Please input the first letter of the selection');

      Writeln('Select shape; Square Rectangle Triangle Circle Quit');

      Write('Requested shape is ');

      Repeat until Keypressed;

      In_Char := ReadKey;

      case UpCase(In_Char) of

       'S' : begin

             Write('Square   Enter length of side ');

             Readln(Length);

             Writeln('The area is ',Area_Of_Square(Length):12:4);

             end;
       'R' : begin

             Write('Rectangle   Enter width ');

             Readln(Width);

             Write('Enter height ');

             Read(Height);

             Writeln('    The area is ',

                            Area_Of_Rectangle(Width,Height):12:4);

             end;
       'T' : begin

             Write('Triangle     Enter base ');

             Readln(Base);

             Write('Enter height ');

             Read(Height);

             Writeln('    The area is ',

                            Area_Of_Triangle(Base,Height):12:3);

             end;
       'C' : begin

             Write('Circle    Enter radius ');

             Readln(Radius);

             Writeln('The area is ',Area_Of_Circle(Radius):12:3);

             end;
       'Q' : Writeln('Quit');

       else Writeln(' undefined entry');

      end;

   until (In_Char = 'Q') or (In_Char = 'q');

end.  (* of main program *)


Result of execution

(The output depends on the data entered at the keyboard)