Subject: Object Oriented Modeling and Design

Difficulty: Medium

Marks: 8 Marks

Object Oriented: It means that we organize software as a collection of discrete objects that incorporate both data structure and behavior.

It includes four aspects:

1. Identity: - It means that data is quantized into discrete, distinguishable entities called object. Objects can be concrete, such as a file system, or conceptual such as scheduling policy in multiprocessing operating system. Each object has its inherent identity.

2. Classification: - Objects with the same data structure (attributes) and behavior (operations) are grouped into a class. A class is an abstraction that describes properties important to an application and ignores the rest.

3. Inheritance: - It is sharing of attributes and operations (features) among classes based on hierarchical relationships. A super class has information that its sub classes refine and elaborate.

4. Polymorphism: - It means that the same operation may behave differently for different classes. The move operation behaves differently for the pawn than for the queen in a chess game.

Object oriented themes:-

(i) Abstraction: - It means focusing on the essential aspects of an entity while ignoring its details. This means focusing on what an object is and does, before deciding how it should be implemented. Use of abstraction during analysis means dealing only with application domain concepts, not making decisions before problem is understood.

(ii) Encapsulation:- It means information hiding. It consists of separating the external aspects of an object, which are accessible to other objects, from internal implementation details of the object, which are hidden from other objects. It prevents program from becoming so interdependent that a small change has massive ripple effect. It gives the ability to combine data structure and behavior in a single entity.

(iii) Combining Data:- The burden of calling code for data execution and operations separately can be minimized by combining data properties and behavioral properties of an entity together. In object oriented program data structure and procedure is defined in single class definition.