DLL编程基础

DLL是组成windows系统的基石，在很多情况下的编程是离不开它的，今天说一下关于DLL编程的一些基础，也是必须要了解的。

主要分为两大类：（1）DLL的编写 （2）DLL的使用

1.DLL的编写

DLL编写需要一个头文件和一个源文件，头文件用于声明，源文件用于实现：

下面是我编写的一个例子程序的头文件中的内容：

// The following ifdef block is the standard way of creating macros which make exporting 
// from a DLL simpler. All files within this DLL are compiled with the TESTDLL_EXPORTS
// symbol defined on the command line. this symbol should not be defined on any project
// that uses this DLL. This way any other project whose source files include this file see 
// TESTDLL_API functions as being imported from a DLL, wheras this DLL sees symbols
// defined with this macro as being exported.
#ifdef TESTDLL_EXPORTS
#define TESTDLL_API __declspec