刚接触vc调试一个程序 编译通过就是 运行是跳如下错误：

LIBCD.lib(crt0.obj) : error LNK2001: unresolved external symbol _main
Debug/WinMain.exe : fatal error LNK1120: 1 unresolved externals
Error executing link.exe.

大哥们帮我看看什么意思啊！
程序是书上的应该没错


是不是我的vc设置有问题啊？？

#include <windows.h>
#include <stdio.h>

LRESULT CALLBACK WinSunProc(
HWND hwnd, // handle to window
UINT uMsg, // message identifier
WPARAM wParam, // first message parameter
LPARAM lParam // second message parameter
);

int WINAPI WinMain(
HINSTANCE hInstance, // handle to current instance
HINSTANCE hPrevInstance, // handle to previous instance
LPSTR lpCmdLine, // command line
int nCmdShow // show state
)
{
WNDCLASS wndcls;

wndcls.cbClsExtra=0;
wndcls.cbWndExtra=0;

wndcls.hbrBackground=(HBRUSH)GetStockObject(BLACK_BRUSH);
wndcls.hCursor=LoadCursor(NULL,IDC_CROSS);
wndcls.hIcon=LoadIcon(NULL,IDI_ERROR);
wndcls.hInstance=hInstance;
wndcls.lpfnWndProc=WinSunProc;
wndcls.lpszClassName="wj2007";
wndcls.lpszMenuName=NULL;
wndcls.style=CS_HREDRAW | CS_VREDRAW;
RegisterClass(&wndcls);

HWND hwnd;
hwnd=CreateWindow("wj2007","my first windows",WS_OVERLAPPEDWINDOW,
0,0,600,400,NULL,NULL,hInstance,NULL);

ShowWindow(hwnd,SW_SHOWNORMAL);
UpdateWindow(hwnd);

MSG msg;
while(GetMessage(&msg,NULL,0,0))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
return 0;
}

LRESULT CALLBACK WinSunProc(
HWND hwnd, // handle to window
UINT uMsg, // message identifier
WPARAM wParam, // first message parameter
LPARAM lParam // second message parameter
)
{

switch(uMsg)
{
case WM_CHAR:
char szChar[20];
sprintf(szChar,"char is %d",wParam);
MessageBox(hwnd,szChar,"weixin",0);
break;
case WM_LBUTTONDOWN:
MessageBox(hwnd,"mouse clicked","weixin",0);
HDC hdc;
hdc=GetDC(hwnd);
TextOut(hdc,0,50,"计算机编程语言培训",strlen("计算机编程语言培训"));
ReleaseDC(hwnd,hdc);
break;
case WM_PAINT:
HDC hDC;
PAINTSTRUCT ps;
hDC=BeginPaint(hwnd,&ps);
TextOut(hDC,0,0,"维新培训",strlen("维新培训"));
EndPaint(hwnd,&ps);
break;
case WM_CLOSE:
if(IDYES==MessageBox(hwnd,"是否真的结束？","weixin",MB_YESNO))
{
DestroyWindow(hwnd);
}
break;
case WM_DESTROY:
PostQuitMessage(0);
break;
default:
return DefWindowProc(hwnd,uMsg,wParam,lParam);
}
return 0;
}