动态链接库(DLL)是一种包含函数和数据的模块。一个DLL可以在运行时被另一个模块(.exe.或者.dll)载入。当一个dll被载入时，它将被映射到调用者进程的地址空间中。
一个dll可以定义两种类型的函数：导出函数和内部函数。导出函数可以被其他模块调用。内部函数只能由定义它的dll在内部使用。虽然dll可以导出数据，但他的数据往往是由他自己的函数缩使用。Dll提供给应用程序一种模块化方案，使得程序功能的更新和重用更加容易。也可以减少内存开销，在多个应用程序，相同的时间使用相同的功能时。因为这些程序可以共享Dll中的代码，尽管每个应用程序有自己的数据副本。
Windows应用程序编程接口（API）就是通过一系列的动态链接库的方式实现的，因此所有使用Windows API的进程都可以使用动态链接。
Dynamic-link libraries (DLL) are modules that contain functions and data. A DLL is loaded at run time by its calling modules (.exe or .dll). When a DLL is loaded, it is mapped into the address space of the calling process.
A DLL can define two kinds of functions: exported and internal. The exported functions can be called by other modules. Internal functions can only be called from within the DLL where they are defined. Although a DLL can export data, its data is usually only used by its functions.
DLLs provide a way to modularize applications so that functionality can be updated and reused more easily. They also help reduce memory overhead when several applications use the same functionality at the same time, because although each application gets its own copy of the data, they can share the code.
The Windows application programming interface (API) is implemented as a set of dynamic-link libraries, so any process that uses the Windows API uses dynamic linking.
