procedure TForm1.Button1Click(Sender: TObject);

var   pw,s:integer;

begin

//  n:=0;  //n是一个全局变量，这里不能给它赋值，否则n就失去全局变量的意义，

           //将导致每次按【确定】按钮，都使n:=0,使n无法累加

  pw:=123456;

  if edit1.text='' then

     s:=0

  else s:=strToInt(edit1.Text);

 

  if n<3 then

    begin

      if s<>pw then

          Begin

            n:=n+1;

            if n=3 then

               Begin

                 edit1.Visible :=false;

                 button1.Visible :=false;

                 button2.Visible :=false;

                 button3.SetFocus ;

                 label1.Visible :=false;

                 label2.Top:=285;

                 label2.Font.Size :=16;

                 label2.Height :=30;

                 label2.Width:=400;

                 label2.Visible :=true;

                 Label2.Caption :='密码错误3次，请【退出系统】！';

               end

            else

              begin

                button2.Visible :=true;

                label2.Font.Color:=clRed;

                label2.Visible :=true;

                Label2.Caption :='第 '+intToStr(n)+' 次密码错误，请重输密码！';

              end;

          end

      else

        begin

          label1.Visible :=false;

          edit1.Visible :=false;

          button1.Visible :=false;

          button2.Visible :=false;

          label2.Height :=30;

          label2.Width:=400;

          label2.Top:=285;

          label2.Font.Size :=16;

          label2.Font.Color :=clgreen;

          label2.Visible :=true;

          Label2.Caption :='密码正确，欢迎使用本系统！';

        end;

    end;

end;