izeOf(TWndClassEx);
  WinClass.lpszClassName:=''MyWindow'';         //类名.
  WinClass.style:=CS_HREDRAW or CS_VREDRAW or CS_OWNDC;
  WinClass.hInstance:=hInst;              //程序的实例句柄.
//设置窗口消息处理函数.
  WinClass.lpfnWndProc:=@MyWinProc;           //窗口过程.
  WinClass.cbClsExtra:=0;                     //以下两个域用于在类结构和Window
s内部保存的窗口结构
  WinClass.cbWndExtra:=0;                     //中预留一些额外空间.
  WinClass.hIcon:=LoadIcon(hInstance,MakeIntResource(''MAINICON''));
  WinClass.hIconsm:=LoadIcon(hInstance,MakeIntResource(''MAINICON''));
  WinClass.hCursor:=LoadCursor(0,IDC_Arrow);
//GetStockObject 获取一个图形对象,在这里是获取绘制窗口背景的刷子,返回一个白色刷
子的句柄.
  WinClass.hbrBackground:=HBRUSH(GetStockObject(white_Brush));
  WinClass.lpszMenuName:=nil;                 //指定窗口类菜单.

//向Windows 注册窗口类.
  if RegisterClassEx(WinClass)=0 then
  begin
    MessageBox(0,''Registeration Error!'',''SDK/API'',MB_OK);
    Exit;
  end;

//建立窗口对象.
  hWnd:=CreateWindowEx(
                 WS_EX_OVERLAPPEDWINDOW,                 //扩展的窗口风格.
                 WinClass.lpszClassName,                 //类名.
                 ''Hello Window'',                         //窗口标题.
                 WS_OVERLAPPEDWINDOW,                    //窗口风格.
                 CW_USEDEFAULT,                          //窗口左上角相对于屏幕
左上角的初始位置x.
  &n