OOPS Features

Class:

 It is a collection of objects.

Object:

It is a real time entity.

An object can be considered a "thing" that can perform a set of related activities. The set of activities that the object performs defines the object's behavior. For example, the hand can grip something or aStudent (object) can give the name or address. In pure OOP terms an object is an instance of a class

The above template describe about object Student

Class is composed of three things name, attributes, and operations

public class student

{

}

student objstudent=new student ();

According to the above sample we can say that Student object, named objstudent, has created out of the student class.

In real world you will often find many individual objects all of the same kind. As an example, there may be thousands of other bicycles in existence, all of the same make and model. Each bicycle has built from the same blueprint. In object-oriented terms, we say that the bicycle is an instance of the class of objects known as bicycles.

Encapsulation:

Encapsulation is a process of binding the data members and member functions into a single unit.

Example for encapsulation is class. A class can contain data structures and methods.

Consider the following class

public class Aperture

{

public Aperture ()

{

}

protected double height;

protected double width;

protected double thickness;

public double get volume()

{

Double volume=height * width * thickness;

if (volume<0)

return 0;

return volume;

}

}

In this example we encapsulate some data such as height, width, thickness and method Get Volume. Other methods or objects can interact with this object through methods that have public access modifier

Abstraction:

Abstraction is a process of hiding the implementation details and displaying the essential features.

Example1: A Laptop consists of many things such as processor, motherboard, RAM, keyboard, LCD screen, wireless antenna, web camera, usb ports, battery, speakers etc. To use it, you don't need to know how internally LCD screens, keyboard, web camera, battery, wireless antenna, speaker’s works.  You just need to know how to operate the laptop by switching it on. Think about if you would have to call to the engineer who knows all internal details of the laptop before operating it. This would have highly expensive as well as not easy to use everywhere by everyone.

So here the Laptop is an object that is designed to hide its complexity.

How to abstract: - By using Access Specifiers

C++ has three access Specifiers

Public -- Accessible outside the class through object reference.

Private -- Accessible inside the class only through member functions.

Protected -- Just like private but Accessible in derived classes also through member 

functions.

Inheritance:

Inheritance is a process of deriving the new class from already existing class

C# is a complete object oriented programming language. Inheritance is one of the primary concepts of object-oriented programming. It allows you to reuse existing code. Through effective use of inheritance, you can save lot of time in your programming and also reduce errors, which in turn will increase the quality of work and productivity. A simple example to understand inheritance in C#.

Polymorphism:

When a message can be processed in different ways is called polymorphism. Polymorphism means many forms.

 

Polymorphism is one of the fundamental concepts of OOP.

 

Polymorphism provides following features: 

• It allows you to invoke methods of derived class through base class reference during runtime.
• It has the ability for classes to provide different implementations of methods that are called through the same name. 

Polymorphism is of two types:
 

1. Compile time polymorphism/Overloading
2. Runtime polymorphism/Overriding

Compile Time Polymorphism

 

Compile time polymorphism is method and operators overloading. It is also called early binding.

 

In method overloading method performs the different task at the different input parameters.

 

Runtime Time Polymorphism

 

Runtime time polymorphism is done using inheritance and virtual functions. Method overriding is called runtime polymorphism. It is also called late binding.

 

When overriding a method, you change the behavior of the method for the derived class.  Overloadinga method simply involves having another method with the same prototype.

 

Caution: Don't confused method overloading with method overriding, they are different, unrelated concepts. But they sound similar.

 

Method overloading has nothing to do with inheritance or virtual methods.

 

Following are examples of methods having different overloads:

 

void area(int side);

void area(int l, int b);

void area(float radius);

Method Overriding:

Whereas Overriding means changing the functionality of a method without changing the signature. We can override a function in base class by creating a similar function in derived class. This is done by usingvirtual/override keywords.

Base class method has to be marked with virtual keyword and we can override it in derived class usingoverride keyword.

Derived class method will completely overrides base class method i.e. when we refer base class object created by casting derived class object a method in derived class will be called.