能帮我解释一下这个基本的delphi代码

你在FORM上拉三个控件，一个EDIT，两个BUTTON。分别双击两个BUTTON。然后在代码编辑器里面，把代码换成下面的。

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    Edit1: TEdit;
    Button1: TButton;
    Button2: TButton;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;
  variable:Integer;
implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
begin
  Inc(variable);
  Edit1.Text:= IntToStr(variable);
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
  Inc(variable,3);
  Edit1.Text:= IntToStr(variable);
end;

end.

F9运行就可以测试到效果了。