Link error 的問題

[6___^]

Visual c++ 5.0 中

Linking...
msvcrtd.lib(crtexe.obj) : error LNK2001: unresolved external symbol
_main
Debug/Cpp1.exe : fatal error LNK1120: 1 unresolved externals
Error executing link.exe.

Cpp1.exe - 2 error(s), 0 warning(s)

要如何解決
source code 如下
.............................
#include <afxwin.h>
class win:public CFrameWnd
{
public:
win()
{
Create(NULL,"HELLO WINDOW");
}
};
class app:public CWinApp
{
virtual BOOL InitIntance();
};
BOOL app::InitIntance()
{
m_pMainWnd= new win();
m_pMainWnd->ShowWindow(m_nCmdShow);
m_pMainWnd->UpdateWindow();
return TRUE ;
}
app w;
_____________________________________
回信
li...@ms1.pclan.com.tw