protected关键字对父子成员变量的影响

 1 include<iostream>
 2 #include<string>
 3 using namespace std;
 4 class parent{
 5 protected:
 6         int mv;
 7 public:
 8         parent(){
 9                 mv = 100;
10         }
11         int value(){
12                 return mv;
13         }
14 };
15 class child:public parent{
16 public:
17         int addvalue(int v){
18                 mv = mv + v;
19         }
20         int changemv(int v){
21                 mv = v;
22         }
23 };
24 int main(){
25         parent p;
26         child c;
27         cout << "c.value()=" << c.value() << endl;//100
28         cout << "p.value()=" << p.value() << endl;//100
29         c.addvalue(250);
30        cout << "c.value()=" << c.value() << endl;//350
31         cout << "p.value()=" << p.value() << endl;//100
32         cout << "c.changemv()后" << endl;
33         c.changemv(380);
34         cout << "c.mv=" << c.value() << endl;//380
35         cout << "p.mv=" << p.value() << endl;//100
36         return 0;
37         }