C++题目：请使用Windows Api写一个window的消息循环。

#include <windows.h>
LRESULT CALLBACK WndProc(HWND,UINT,WPARAM,LPARAM);
int WINAPI WinMain(HINSTANCE hINstance,
HINSTANCE hPrevInstance,
LPSTR lpszCmdParam,
int nCmdShow)
{
static char szAppName[]="xianshi";
HWND hwnd;
MSG msg;
WNDCLASS wndclass;
if(! hPrevInstance)
{
wndclass.style = CS_HREDRAW | CS_VREDRAW;
wndclass.lpfnWndProc = WndProc;
wndclass.cbClsExtra=0;
wndclass.cbWndExtra=0;
wndclass.hInstance=hINstance;
wndclass.hIcon = LoadIcon(NULL,IDI_APPLICATION);
wndclass.hCursor = LoadCursor(NULL,IDC_ARROW);
wndclass.hbrBackground=(HBRUSH)GetStockObject(LTGRAY_BRUSH);
wndclass.lpszMenuName = NULL;
wndclass.lpszClassName = szAppName;
RegisterClass(&wndclass);
}
hwnd=CreateWindow(
szAppName,
"The XianShi",
WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT,CW_USEDEFAULT,
CW_USEDEFAULT,CW_USEDEFAULT,