定义一个字符串类String，其私有成员为一个字符串指针。设计构造函数，拷贝构造函数，析构函数，设置新值函数Set, 打印成员值函数Print。借助此String类，将操作符＂＝＝＂、＂＞＂、＂＜＂的重载函数设置为String类的成员函数，实现对操作符＂＝＝＂、＂＞＂、＂＜＂的重载，使之能直接比较两个String类类型的字符串的大小，设计各种情况调用此三个重载操作符。-definition of a string type String, its private members as a string pointer. Design Constructors, the copy constructor and destructor function, install a new function Set, members of Print Print function. String through this type of operator "==",">", "" "Heavy function set to the String class member function, the operator realized "==",">", "" "heavy, so that it can direct comparison of two types of Class String string size, Design of various call this three heavy-duty operator.