What is a pure virtual function in C++?

Answer:

A pure virtual function (or abstract function) in C++ is a virtual function for which we don’t have an implementation, we only declare it. A pure virtual function is declared by assigning 0 in the declaration.  We can not instantiate the abstract class and we have to define it in the derived class.

Let see the below example.

#include<iostream>
using namespace std;
class Base
{
public:
    //pure virtual function
    virtual void fun() = 0;
};
class Child: public Base
{
public:
    void fun()
    {
        cout << "Child class fun is called";
    }
};
int main()
{
    Child d;
    d.fun();
    return 0;
}

Output: Child class fun is called