163: Mainline

Member-function definitions differ from ordinary function definitions in the following respects:

• Member functions have no parameter corresponding to the special, class-object argument.
• In member functions, there are no parameters or variables connected to member variables via the class-member operator; instead, all member variables are taken to belong to the special, class-object argument.

Thus, you define volume as a member function as follows:

class box_car { 
  public: double height, width, length; 
          double volume ( ) { 
            return height * width * length; 
          } 
}; 

When this volume member function is called on a particular box_car object, the height, width, and length variables appearing in the definition of volume automatically refer to the height, width and length member variables associated with that particular box_car object.