类的hello，world

写类的hello，world程序 如下

#include <iostream>using namespace std;#include <string.h>class A{    protected:    string a;    public:        A(){                a ="hello,world";        }        string  get_a(){            return a;        }};class B : public A{};int main(){        B b;        cout<<b.get_a()<<endl;;}