全局变量与局部变量

 1 unit Unit1;
 2 interface
 3 uses
 4   Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
 5   Dialogs, StdCtrls;
 6 type
 7   TForm1 = class(TForm)
 8     Button1: TButton;
 9     Button2: TButton;
10     procedure Button1Click(Sender: TObject);
11     procedure Button2Click(Sender: TObject);
12   private
13     { Private declarations }
14   public
15     { Public declarations }
16   end;
17 var
18   Form1: TForm1;
19 implementation
20 {$R *.dfm}
21 //全局变量
22 var
23   gLobal_int:Integer;
24   Global_p:pchar;
25 procedure TForm1.Button1Click(Sender: TObject);
26 begin
27  if @Global_int <>nil then
28  begin
29    ShowMessage('global_int己被分配内存');
30    showmessage(IntToStr(global_int));
31    end;
32    if global_p=nil then
33    begin
34      ShowMessage('global_p没有被分配内存');
35      ShowMessage(global_p);
36    end;
37  end;
38  //局部变量
39 procedure TForm1.Button2Click(Sender: TObject);
40 var
41   local_int,local_int2:Integer;
42   oldaddr,newaddr:Integer;
43   local_p:PChar;
44 begin
45 oldaddr:=Integer(@local_int);
46 local_int:=7;
47 newaddr:=Integer(@local_int);
48 if oldaddr=newaddr then
49 ShowMessage('地址值没有变化，声明local_int时就分配内存');
50 ShowMessage(IntToStr(local_int2));
51 if local_p <>nil then
52 ShowMessage(local_p);
53 end;
54 end.