windows程序链接错误

#include <windows.h>
#include <stdio.h>
LRESULT CALLBACK WindowProc( HWND hwnd,
UINT uMsg,
WPARAM wParam,
LPARAM lparam);
int WINAPI WinMain( HINSTANCE hInstance,
HINSTANCE hPrevInstance,
LPSTR lpCmdLine,
int nCmdShow)
{
WNDCLASS wndcls;
wndcls.cbClsExtra = 0; //类的附加属性
wndcls.cbWndExtra = 0; //窗口的附加属性
wndcls.hbrBackground =(HBRUSH)GetStockObject(BLACK_BRUSH); //画刷
wndcls.hCursor = LoadCursor(NULL,IDC_CROSS); //鼠标样式
wndcls.hIcon = LoadIcon(NULL,IDI_ERROR); //图标样式
wndcls.hInstance = hInstance; //实例句柄
wndcls.lpfnWndProc = WindowProc; //窗口过程函数
wndcls.lpszClassName = "chuangkou"; //类名
wndcls.lpszMenuName = NULL; //菜单名
wndcls.style = CS_HREDRAW | CS_VREDRAW ;//类型，水平重画，垂直重画
RegisterClass(&wndcls); //注册窗口
HWND hwnd; hwnd=CreateWindow("chuangkou","我的窗口",WS_OVERLAPPEDWINDOW,
0,0,800,1000,NULL,NULL,hInstance,NULL); //创建窗口
ShowWindow(hwnd,SW_SHOWNORMAL);//显示窗口
UpdateWindow(hwnd);//更新窗口
MSG msg;
while(GetMessage(&msg,NULL,0,0))//从消息队列中获取所有窗口消息
{
TranslateMessage(&msg);//消息转换
DispatchMessage(&msg);//回调
}
return 0;
}
LRESULT CALLBACK WindowProc( HWND hwnd, //窗口句柄
UINT uMsg, //消息标识
WPARAM wParam,//消息附加参数
LPARAM lparam //第二个消息的附加参数
)
{
switch(uMsg)
{
case WM_CHAR:
break;
case WM_LBUTTONDOWN:
break;
case WM_PAINT:
break;
case WM_CLOSE:
break;
case WM_DESTROY:
break;
default:
return DefWindowProc(hwnd,uMsg,wParam,lparam);
}
return 0;
}Deleting intermediate files and output files for project 'winmain - Win32 Debug'.
--------------------Configuration: winmain - Win32 Debug--------------------
Compiling...
winmain.cpp
Linking...
LIBCD.lib(crt0.obj) : error LNK2001: unresolved external symbol _main
Debug/winmain.exe : fatal error LNK1120: 1 unresolved externals
执行 link.exe 时出错.
winmain.exe - 1 error(s), 0 warning(s)