6.Object Oriented Concepts

                    

Ø Software developed using object oriented methodology are proclaimed to be more reliable, easier to maintain, reuse and enhance.

Ø Object oriented concepts started creation of new software originating in the 1960s. since mid 1980s,  It had become the main main programming paradigm used in the creation of new software.

Ø Popular programming language that support oop are C++, Java, C#, VB.net, ASP.net and PHP.

Ø The way of programming language divided to two categories:

    1.structure/procedural         2. Object oriented.

Ø Procedural programming language focus is on writing function and procedures which operate on data.

Ø Object oriented programming focus is on object which contain both data and  functionality.

Ø Power of object oriented programming language enables the programmer modular, reusable and extendable code.

Ø Oop uses object as its fundamental building block    similar object classified using concept of class.Object are the entities of which the world comprised( e.g. Car, person, time, date etc.).

Ø Object oriented support four specific characteristics: 1.abstraction, 2.encapsulation, 3.polymorphism, 4.inheritance

Ø Characteristics are Known as Properties or Attributes.

Ø Object identify by use of value. Values are called State (In OOP).

Ø Behavior associated with Object .Behavior is is known as method or features.

Ø Object Oriented system uses the concept of class.

·        Enables to express the set of objects.

·        considered blue print for various objects.

·        template for multiple objects with similar features.

Ø Unified Modeling Language(UML): Used to create models of object oriented software to help with design of an application.

Ø UML is visual modeling Language.UML defined and maintained by Object Management Group(OMG).

Ø Class Diagram is to model the static view of an Application.Represent using icon rectangle split into three section: 1. Class ame, 2.Attributes or properties, 3.Behavior or methods or operations.

(Note- [ ] square bracket Optional Add Item enclosed between < > angle bracket)

Ø UML notation an attribute is declared using syntax:

[<visibility>]<attrityute name>[:<attribute data type> [=<initial value>]]

Ø  Visibility can be 1.Private ( - ),     2. Protected ( # ),      3.Public (+ ),   4. Packege ( ~ ).

Ø Attribute generally refers to Variable (E.g. name, date(it means data field))

Ø UML notation an operation is declared using syntax:        

[<visibility>]<method name>( parameter list separated by comma ):<return type>

Ø Computer Program two core elements: Data and functions

·        Structured/Procedural Programming Language two core elements as two separate entities.

·        Object Programming Language two core elements as a single entity.

Ø Encapsulation: The mechanism providing protection of data and methods of a program is called encapsulation.

·        Data hiding Capabilities, wrapping data method into single unit, data safe from unintended action and inadvertent access by outside objects.

Ø Data Abstraction: Hide complexity, relies on the separation of interface and implementation, Provide skeleton and templates for our use.(Ex. Television Set)

·        ADT(Abstract Data Types) or structures (struct) in C/C++, Classes in C++/Java are examples of  Data abstraction.

Ø Messaging: In Object Oriented terminology a call a method to referred to as a message

Ø Polymorphism means “many form”. There may be different form of single method or operation.

·        Polymorphism is achieved using two types of overloading 1.Method Overloading , 2.Operator Overloading.

Ø Aggregation and Composition: When object of one class composed of objects of other class, it is called aggregation or composition.

·        It represent  ‘has-a’ or ‘a-part of’ relationship between classes.

·        Aggregation: (Empty Diamond symbol) Non-exclusive relationship between two class.

·        Composition: (Filled Diamond symbol) exclusive relationship between two class.

·        The class that contains objects of other class is known as Owner class, whole class or aggregating class.

·        The class is contained in owner class is known as subject class, part class and aggregated class.

Ø Inheritance refers to the capability of defining a new class of objects that inherits the characteristics of  another existing class.

·        Generalization is another name of inheritance or ‘is-a kind of’ relationship between two class.

·        In Object Oriented terminology new class is called Sub class, Child class and Derived class.

·        In Object Oriented terminology existing class is called Super class, Parent class and Base class.

·        When a class derived from two or more class. It  is known as multiple inheritance.