http://blog.csdn.net/baozi3026/article/details/5353720
本打算了解一下纖程內容，在試圖使用 ConvertThreadToFiber的時候，編譯總是出錯，提示信息如下：error C2065: 'ConvertThreadToFiber' : undeclared identifier，編譯器告訴我“函數未聲明”。於是轉而查看MSDN，有內容如下：
Requirements:
Windows NT/2000: Requires Windows NT 3.51 SP3 or later.
Windows 95/98: Requires Windows 98.
Header: Declared in Winbase.h; include Windows.h.
Library: Use Kernel32.lib.
但明明已經#include <Windows.h>了。不得已，又經Windows.h進入Winbase.h中，查看源碼，見聲明之前有條件編譯語 句：#if(_WIN32_WINNT >= 0x0400)，由此發現我的程序並沒有聲明宏_WIN32_WINNT。最終在StdAfx.h文件的#include <windows.h>語句之前添加語句：
#define _WIN32_WINNT 0x0400
編譯通過。
理解_WIN32_WINNT的作用：
需要你自已在stdafx.h頭文件中定義。編譯器根據此宏來確定windows的版本，如果你需要使用高版本的WIN32函數,只有你定義了此宏後才能使用
Windows XP _WIN32_WINNT>=0x0501
Windows 2000 _WIN32_WINNT>=0x0500
Windows NT 4.0 _WIN32_WINNT>=0x0400
Windows Me _WIN32_WINDOWS=0x0490
Windows 98 _WIN32_WINDOWS>=0x0410
Internet Explorer 6.0 _WIN32_IE>=0x0600
Internet Explorer 5.01, 5.5 _WIN32_IE>=0x0501
Internet Explorer 5.0, 5.0a, 5.0b _WIN32_IE>=0x0500
Internet Explorer 4.01 _WIN32_IE>=0x0401
Internet Explorer 4.0 _WIN32_IE>=0x0400
Internet Explorer 3.0, 3.01, 3.02 _WIN32_IE>=0x0300
PS:當然也可以在程序的C++的預處理器中設置。
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MSDN中的描述
Using the SDK Headers
This version of the Microsoft® Platform SDK enables you to create applications that run on Microsoft Windows® 95, Microsoft Windows NT® 4.0, Windows® 98, Windows Millennium Edition (Windows Me), Windows 2000, Windows XP, and Windows .NET Server 2003 family. You can also create 64-bit applications. The header files use data types that allow you to build both 32- and 64-bit versions of your application from a single source code base. For more information, see Getting Ready for 64-bit Windows.
Microsoft® Visual C++® includes content from the edition of the Platform SDK that was current at the time Visual C++ was released. Therefore, if you install the latest Platform SDK, you may end up with multiple versions of the same header files on your computer. To ensure that you are using the latest version of the SDK header files, follow the directions included in Installing the Platform SDK with Visual Studio. Otherwise, you will receive the following error when compiling code that uses features that were introduced after Visual C++ was released: error C2065: undeclared identifier.
Certain functions that depend on a particular version of Windows are declared using conditional code. This enables you to use the compiler to detect whether your application uses functions that are not supported on its target version(s) of Windows. To compile an application that uses these functions, you must define the appropriate macros. Otherwise, you will receive the C2065 error message. The following table indicates the macros you must define to target each system.
Minimum system required Macros to define
Windows .NET Server 2003 family _WIN32_WINNT>=0x0502
Windows XP _WIN32_WINNT>=0x0501
Windows 2000 _WIN32_WINNT>=0x0500
Windows NT 4.0 _WIN32_WINNT>=0x0400
Windows Me _WIN32_WINDOWS=0x0490
Windows 98 _WIN32_WINDOWS>=0x0410
Internet Explorer 6.0 _WIN32_IE>=0x0600
Internet Explorer 5.01, 5.5 _WIN32_IE>=0x0501
Internet Explorer 5.0, 5.0a, 5.0b _WIN32_IE>=0x0500
Internet Explorer 4.01 _WIN32_IE>=0x0401
Internet Explorer 4.0 _WIN32_IE>=0x0400
Internet Explorer 3.0, 3.01, 3.02 _WIN32_IE>=0x0300
For example, to use the features specifically marked for Windows 2000 in the header files, you need to explicitly define _WIN32_WINNT as 0x0500 or greater. You can define the symbols using the #define statement in each source file, or by specifying the /D_WIN32_WINNT=0x0500 compiler option supported by Visual C++.
Visual C++ 6.0: To specify compiler options, Go to the Projects menu and click Settings, then select the C/C++ tab.
Visual C++ 7.0: To specify compiler options, go to the Projects menu and click Properties.
The macros in Win32.mak can help you define the correct macros. The value of _WIN32_WINNT depends on the platform you choose to target. For more information, see Building Applications Using Win32.mak.