header files:

#include <string>         // use String Object you should leading-in it (ps:not string.h,the string.h is belong to the C)

#include <iostream>     // the input and output of C++。

using namespace std;

the output and input of String should use the function cin and cout. (ps:cout not count).

Thanks for the XFreedom

http://www.cnblogs.com/xFreedom/archive/2011/05/16/2048037.html