friend                  Object Scope Modifier

 friend identifier;

    A friend can be either an object or a class that, while not a member
    of another class, can access fully any private and protected members
    of that class.

   -------------------------------- Example ---------------------------------

  class birds {
     friend bees;
     int num_finches;
     int increment_num_finches(void);
  };
  class bees {
     int num_honeybees;
     int increment_num_honeybees(void);
   }