Why do we need virtual functions in C++?

Question

I\'m learning C++ and I\'m just getting into virtual functions.

From what I\'ve read (in the book and online), virtual functions are functions in the base class that

Answer 1

Need for Virtual Function explained [Easy to understand]

#include

using namespace std;

class A{
public: 
        void show(){
        cout << " Hello from Class A";
    }
};

class B :public A{
public:
     void show(){
        cout << " Hello from Class B";
    }
};


int main(){

    A *a1 = new B; // Create a base class pointer and assign address of derived object.
    a1->show();

}

Output will be:

Hello from Class A.

But with virtual function:

#include

using namespace std;

class A{
public:
    virtual void show(){
        cout << " Hello from Class A";
    }
};

class B :public A{
public:
    virtual void show(){
        cout << " Hello from Class B";
    }
};


int main(){

    A *a1 = new B;
    a1->show();

}

Output will be:

Hello from Class B.

Hence with virtual function you can achieve runtime polymorphism.