[marcoszorrilla]

Código Delphi [-]
unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  StdCtrls;

  function mul(x:integer):integer;
type
  TForm1 = class(TForm)
    Button1: TButton;
    Label1: TLabel;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public

    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.DFM}

function mul(x:integer):integer;
begin
mul:=(x*x);
end;
procedure TForm1.Button1Click(Sender: TObject);
var
a:integer;
begin

a:=mul(3);
label1.Caption:=inttostr(a);
end;

end.

Un Saludo.