继承

#include <iostream>using namespace std;class A{public :A(){a = 1;}void display(){cout << "a"<< a <<" ";}protected:void increase(){a++;}private:int a;};class B:public A{public:B(){increase();}protected:};class C:public A,B{}int main(){A a;a.display();B b;b.display();cout << "   " << endl;}