delphi编程求N的阶乘

计算阶乘，可按回车键计算
unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    Button1: TButton;
    Button2: TButton;
    Edit1: TEdit;
    Edit2: TEdit;
    Label1: TLabel;
    Label2: TLabel;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Edit1KeyUp(Sender: TObject; var Key: Word;
      Shift: TShiftState);
  
   
  private
    { Private declarations }
  public
    { Public declarations }
  end;



var
  Form1: TForm1;

implementation

{$R *.dfm}
function jiecheng(n:integer):integer;
begin
   if (n=0) or (n=1) then
      result:=1
   else
      result:=jiecheng(n-1)*n;
end;


procedure TForm1.Button1Click(Sender: TObject);
begin
    try
       if (strtoint(edit1.Text)>=0) and (strtoint(edit1.Text)<10) then
          edit2.Text:=inttostr(jiecheng(strtoint(edit1.text)))
       else
         begin
          edit2.Clear;
          showmessage('输入数不在0-9之间');
         end;
    except
       showmessage('输入数错误');
end;
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
    close;
end;

procedure TForm1.Edit1KeyUp(Sender: TObject; var Key: Word;
  Shift: TShiftState);
begin
    if key=vk_return then
     try
       if (strtoint(edit1.Text)>=0) and (strtoint(edit1.Text)<10) then
          edit2.Text:=inttostr(jiecheng(strtoint(edit1.text)))
       else
         begin
          edit2.Clear;
          showmessage('输入数不在0-9之间');
         end;
    except
       showmessage('输入数错误');
end;
end;

end.