virtual function

#include <iostream>
using namespace std;

class A
{
public:
    void display() {}
};

class B : public A
{
public:
    virtual void display()
    {
        cout << "\nDisplay function of B Class";
    }
};

class C : public A
{
public:
    virtual void display()
    {
        cout << "\nDisplay function of C Class";
    }
};

class D: public B, public C{
    public:
    void display(){
        cout << "\nDisplay function of D Class, since B & C class have virtual functions";
    }
};

int main()
{
    B *aa;
    D obj;
    aa= &obj;
    aa->display();
    return 0;
}