How to make abstract class in c++

C++ has no abstract keyword or equivalent, to make a class abstract is to declare a pure virtual function in it (which prevents instantiation).

For this same reason, in C++ there is not much difference between an  interface and an abstract class - a C++ interface is simply a class containing only pure virtual functions.

C++ has no keyword abstract. However, you can write pure virtual functions; that's the C++ way of expressing abstract classes.

What is a Pure Virtual Function:
A Pure Virtual Function is a Virtual function with no body.

Declaration  of Pure Virtual Function:
Since pure virtual function has no body, the programmer must add the notation =0 for declaration of the pure virtual function in the base class.

Syntax of Pure Virtual Function:
class class_name //This denotes the base class of C++ virtual function
{
    public:
    virtual void virtualfunctioname() = 0 //This denotes the pure virtual function in C++
};
___________________________________________________________________
//Full code example
#include <iostream>
using namespace std;
class Sandeep
{
public:
        virtual void example()=0; //Denotes pure virtual Function Definition
};

class Demo1:public Sandeep
{
public:
        void example()
        {
                cout << " \n Welcome";
        }
};

class Demo2:public Sandeep
{
public:
        void example()
        {
                cout << " To My blog \n";
        }
};

int main()
{
        Sandeep* arra[2];
        Demo1 d1;
        Demo2 d2;
        arra[0]=&d1;
        arra[1]=&d2;
        arra[0]->example();
        arra[1]->example();
}

OUTPUT: