Pascal/Turbo Pascal - hacer un programa para determinar las palabras palindromes

uses crt;

     var

       palabra : string[25];

       Ch: Char;

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

     (* Function alreves             *)

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

     function voltear(S: string): string;

     var

       I, y : Integer;

       aux : string[25] ;

     begin

        aux := '';

        y  := 0;

      for I := Length(S) downto 1 do

      begin

          y := y + 1;

          aux := aux + S[I];

       end;

          voltear := aux;

      end;

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

     (* Function alreves             *)

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

     function sino(S1: string): string;

     var

       I, y : Integer;

       aux : string[25] ;

     begin

       if (S1 = voltear(S1))  then

       begin

         sino := 'Si';

       end

       else

       begin

          sino := 'No';

       end;

      end;

     begin

      (********************************);

      (* programa principal           *);

      (********************************);

     repeat

       clrscr;

       gotoxy(20,5);

       write('Ingrese una palabra: ');

       gotoxy(41,5);

       readln(palabra);

       gotoxy(20,7);

       write('la palabra es: ', palabra ,' ' , sino(palabra),' ','es palindrome');

          gotoxy(20,9);

        write('Desea continuar [S/N]: ');

              Ch := readkey ;

     until (upcase(Ch) <> 'S');

end.