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