Static data members

• Class members may be declared static

• Static data members belong to the class, not to any object...
  ...so they don't take up space in objects.

• All objects share the same variable, like a global, but in the class scope:

  
  // point.h
  class Point
  {
      static int m_x_origin;
      static int m_y_origin;
      int m_x;
      int m_y;
      //...
  };
  
  // point.cpp:
  int Point::m_x_origin = 0; // initialization of private (!) static members
  int Point::m_y_origin = 0;