Virtual Base Class in C++

Program 1

// Virtual Class in CPP
#include<iostream>
using namespace std;
class A
{
    public:
    void display()
    {
        cout<<"Hello Display Method";
    }
};
class B:virtual public A{};

class C:public virtual A{};

class D:public B,public C
{};

int main()
{
    system("cls");
    D D1;
    D1.display();
    return 0;
}