#include<iostream>
using namespace std;//public 修饰的成员便俩个和方法都能使用
//protected：类的内部 在继承的子类中可使用
class Parents
{
public:int a;//名字
protected:int b;//密码
private:int c;//情人public:void printT(){cout << "printT" << endl;}
};
class Children1 :public Parents
{
public:void useVar(){a = 0;b = 0;//c = 0;//private}
};//私有继承
class Children2 :private Parents
{
public:void useVar(){a = 0;b = 0;//c = 0;//private}
};class Children3 :protected Parents
{
public:void useVar(){a = 0;//okb = 0;//ok//	c = 0;}
};//void main01()
//{
//	Parents t1, t2;
//	t1.a = 10;
//	//t1.b = 30;//err
//	//t2.c = 30;//err
//
//
//	return;
//}
void main02()
{Children2 c2;//c1.a = 10;//err//c2.b = 30;//err//c3.b = 20;//err
}
void main()
{Children3 c3;//c3.a = 10;//err//c3.b = 30;//err//c3.c = 20;//err
}

调用原则：

#include<iostream>
using namespace std;
class Parent
{
public:Parent(int a, int b){this->a = a;this->b = b;cout << "父类构造" << endl;}~Parent(){cout << "父类析构" << endl;}void printP(int a, int b){this->a = a;this->b = b;cout << "father" << endl;}
private:int a;int b;};
class  child :public Parent
{
public:child(int a, int b, int c) :Parent(a, b){this->c = c;}~child(){cout << "discont" << endl;}void printC(){cout << "son" << endl;}
private:int c;
};void play()
{child c1(1, 2, 3);
}void main()
{//Parent p(1, 2);//child c1(1, 2, 3);play();return;
}

//#include <iostream>
//#include <string>
//using namespace std;
//
//class Object
//{
//public:
//    Object(int a, int b) : a(a), b(b)
//    {
//        cout << "obj a: " << a << " b: " << b << endl;
//    }
//
//protected:
//    int a;
//    int b;
//};
//
//class Parent : public Object
//{
//public:
//    Parent(const string& p) : Object(1, 2), obj1(3, 4), obj2(5, 6), p(p)
//    {
//        cout << p << endl;
//        cout << "父类构造" << endl;
//    }
//
//    ~Parent()
//    {
//        cout << "父类析构" << endl;
//    }
//
//    void printP(int a, int b)
//    {
//        cout << "father" << endl;
//    }
//
//protected:
//    string p;
//    Object obj1;
//    Object obj2;
//};
//
//class child : public Parent
//{
//public:
//    child(const string& p) : Parent(p), obj1(3, 4), obj2(5, 6), myp(p)
//    {
//
//    }
//
//    ~child()
//    {
//        cout << "discont " << myp << endl;
//    }
//
//    void printC()
//    {
//        cout << "son " << myp << endl;
//    }
//
//private:
//    string myp;
//    Object obj1;
//    Object obj2;
//};
//
//int main()
//{
//    child c1("继承");
//    c1.printC();
//    return 0;
//}

 ![在这里插入图片描述](https://i-blog.csdnimg.cn/direct/b1d26ed362de44ffaeb548db15445a19.png)继承二义性
![在这里插入图片描述](https://i-blog.csdnimg.cn/direct/50aae96b141d473eb4c7437b1e80e780.png)
![在这里插入图片描述](https://i-blog.csdnimg.cn/direct/374ee3c6f68a408eb91ddb4f859074c6.png)