C编写，实现字符串摘要、文件摘要两个功能。

里面主要包含3个文件: Md5.cpp、Md5.h、Main.cpp。其中Md5.cpp是算法的代码，里的代码大多是从 rfc-1321 里copy过来的；Main.cpp是主程序。-C to prepare, to achieve string summary document containing a summary of the two functions. 3 inside the main document contains: Md5.cpp, Md5.h, Main.cpp. Md5.cpp which is the algorithm code, in most of the code is in rfc-1321 from the copy back　Main.cpp is the main program.