protected关键字对父子成员变量的影响

include<iostream>
#include<string>
using namespace std;
class parent{
protected:
        int mv;
public:
        parent(){
                mv = 100;
        }
        int value(){
                return mv;
        }
};
class child:public parent{
public:
        int addvalue(int v){
                mv = mv + v;
        }
        int changemv(int v){
                mv = v;
        }
};
int main(){
        parent p;
        child c;
        cout << "c.value()=" << c.value() << endl;//100
        cout << "p.value()=" << p.value() << endl;//100
        c.addvalue(250);
       cout << "c.value()=" << c.value() << endl;//350
        cout << "p.value()=" << p.value() << endl;//100
        cout << "c.changemv()后" << endl;
        c.changemv(380);
        cout << "c.mv=" << c.value() << endl;//380
        cout << "p.mv=" << p.value() << endl;//100
        return 0;
        }

运行结果：

c.value()=100
p.value()=100
c.value()=350
p.value()=100
c.changemv()后
c.mv=380
p.mv=100

结论：

对于具有继承关系的类，父类和子类各自有各自的成员变量，子类对其成员变量的修改并不会影响父类的