用C++寫程序，肯定要用預編譯頭文件，就是那個
stdafx.h.
不過我一直以為只要在.cpp文件中包含stdafx.h 就使用了預編譯頭文件，其實不對。
在VC++中，預編譯頭文件是指放到stdafx.h中的頭文件才會有效果。
如下： file: stdafx.h
代碼如下：
// stdafx.h : include file for standard system include files,
// or project specific include files that are used frequently, but
// are changed infrequently
//
#pragma once
#ifndef _WIN32_WINNT // Allow use of features specific to Windows XP or later.
#define _WIN32_WINNT 0x0501 // Change this to the appropriate value to target other versions of Windows.
#endif
#define WIN32_LEAN_AND_MEAN // Exclude rarely-used stuff from Windows headers
代碼如下：
// 各位注意，要想使用預編譯效果的頭文件要放這裡。
#include <Windows.h>
#include "xxx.h"
代碼如下：
// TODO: reference additional headers your program requires here
在stdafx.cpp中保持不變即可，默認如下：
代碼如下：
// stdafx.cpp : source file that includes just the standard includes
// CPPTestHelper.pch will be the pre-compiled header
// stdafx.obj will contain the pre-compiled type information
#include "stdafx.h"
// TODO: reference any additional headers you need in STDAFX.H
// and not in this file
