简单vc++窗口程序问题

#include<windows.h>
LRESULT CALLBACK WndProc(HWND,UINT,WPARAM,LPARAM);
int WINAPI WinMain(HINSTANCE hInstance,HINSTANCE hPrevInst,LPSTR lpszCmdLine,int nCmdShow)
{
HWND hwnd;
MSG Msg;
WNDCLASS wndclass;
char lpszClassName[]="WINDOW";
char lpszTitle[]="My_Windows";

wndclass.style=0;
wndclass.lpfnWndProc=WndProc;
wndclass.cbClsExtra=0;
wndclass.hInstance=hInstance;
wndclass.hIcon=LoadIcon(NULL,IDI_APPLICATION);
wndclass.hCursor=LoadCursor(NULL,IDC_ARROW);
wndclass.hbrBackground=GetStockObject(BLACK_BRUSH); //返回不是 BRUSH要强制转换wndclass.hbrBackground=(HBRUSH)GetStockObject(BLACK_BRUSH);
wndclass.lpszMenuName=NULL;
wndclass.lpszClassName=lpszClassName;

if(!RegisterClass(&wndclass))
{
MessageBeep(0); return FALSE;
}

hwnd=CreateWindow
(
lpszClassName,
lpszTitle,
WS_OVERLAPPEDWINDOW,
CW_USED