C++ program to use Static data member and Static member functions

#include <iostream>
using namespace std;
class ABC
{
        static int a; //a=0 internally by default
    public:
        void increase()
        {
            a++;
        }
        void display()
        {
            cout<<endl<<"a="<<a;
        }
};

int ABC::a; //static member variable definition

int main()
{
    ABC ob1,ob2,ob3;
    ob1.increase();
    ob2.increase();
    ob3.increase();
    ob1.display();
    ob2.display();
    ob3.display();
    return 0;
}