Object-oriented Programming Terminology

• Object: typically refers to an instance (although classes may be objects too).

• Class: a description of a set of similar objects, the instances. This description typically includes:
  • Instance variable descriptions: the names and types of variables that are assumed to be defined for every subclass or instance of the class.

  • Methods: mapping from the selector or abstract name of the method to the specific function that implements the method for the class.

    
            draw:    circle_draw()
    

• Instance: an individual member of a class. Typically an instance is a member of exactly one class. An instance is a record that:
  • can be identified as being an object
  • denotes the class to which the object belongs
  • contains the instance variables
• Superclass: a class to which a given class belongs. Sometimes a class may have more than one superclass.