Object Oriented Design (OOD)

(OOD) A design method in which a system is modelled as a collection of cooperating objects and individual objects are treated as instances of a class within a class hierarchy. Four stages can be identified: identify the classes and objects, identify their semantics, identify their relationships and specify class and object interfaces and implementation. Object-oriented design is one of the stages of object-oriented programming.

object -  an instance of the data structure and behaviour defined by the object's class. Each object has its own values for the instance variables of its class and can respond to the methods defined by its class.

method - A line-oriented Smalltalk for PC's, produced by Digitalk ca 1985. Methods was the predecessor of Smalltalk/V.

class - a set of objects which share a common structure and behaviour. The structure of a class is determined by the class variables which represent the state of an object of that class and the behaviour is given by a set of methods associated with the class.

subclass - a class that is derived from a base class by inheritance. The derived class contains all the features of the base class, but may have new features added or redefine existing features.

base class -  The class from which another class (a "subclass") inherits, the class it is based on.
"base class" is the term used in C++.  (or superclass).

inheritance - the ability to derive new classes from existing classes. A derived class (or "subclass") inherits the instance variables and methods of the "base class" (or "superclass"), and may add new instance variables and methods.

instance - While a class is just the type definition, an actual usage of a class is called "instance". Each instance of a class can have different values for its instance variables, i.e. its state.

derived class - a class that is derived from a base class by inheritance. The derived class contains all the features of the base class, but may have new features added or redefine existing features.

Smalltalk - The pioneering object-oriented programming system developed in 1972 by the Software Concepts Group, led by Alan Kay, at Xerox PARC between 1971 and 1983. It includes a language, a programming environment, and an extensive object library.Smalltalk took the concepts of class and message from Simula-67 and made them all-pervasive. Innovations included the bitmap display, windowing system, and use of a mouse.