这是我从一本书上抄的程序，为什么我和书上的一样会没法运行呢？ unit log;

interface

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

type Tlogform = class(TForm) Edtusername: TEdit; user: TLabel; password: TLabel; Edtpassword: TEdit; Btnok: TButton; procedure BtnokClick(Sender: TObject); private { Private declarations } public { Public declarations } end;

var logform: Tlogform;

implementation

{$R *.dfm}

procedure Tlogform.BtnokClick(Sender: TObject); const username:string=''; password:string=''; begin if not(Edtusername.Text=username)then begin showmessage('输入的用户名错误，请重新输入!'); Edtusername.Text:=''; Edtusername.SetFocus; end else if not(Edtpassword.Text=password)then begin showmessage('输入的密码错误，请重新输入!'); Edtpassword.Text:=''; Edtpassword.SetFocus; end else begin guessfm.Show; log.Hide; end; end;

end.