A static member variable example.
#include <iostream>
using namespace std;

class myclass {
  static int i;
public:
  void setInt(int n) { 
     i = n; 
  }
  int getInt() { 
     return i; 
  }
};


int myclass::i;           // Definition of myclass::i. i is still private to myclass.

int main()
{
  myclass object1, object2;

  object1.setInt(10); 

  cout << "object1.i: " << object1.getInt() << '\n'; // displays 10
  cout << "object2.i: " << object2.getInt() << '\n'; // also displays 10 

  return 0;
}