Chapter 5 - Object Oriented Programming : Computer Sci NEB Class 12

What is OOP?

OOP (Object-Oriented Programming) is a programming paradigm which focuses on data rather than procedure. It supports inheritance, so it is easy to reuse the code.

1. Programming Paradigms: Procedural, Structural and Object-Oriented

Differentiate between OOP and Structured Programming language (POP)

2. Features of OOP

The features of OOP are as follows:

a. Class

A class is the collection of similar kinds of objects. A class is a data type. It is a template that unites member data and member functions. It is the prototype or model. It does not occupy memory location. A class is the well description of object.

Example: vehicle class

• Attributes (member data): Name, model, color, height
• Behaviours (member functions): start(), stop(), accelerate()

b. Object

An object may be a person, a place, a bank account, or any item that the program must handle. An object is an instance of a class. It gives life to a class. It occupies memory location.

c. Encapsulation

The wrapping up of member data and member function into a single unit is called encapsulation. The data is not accessible from outside of class. That is, data can be hidden making them private so that it is safe from accidental alteration. Only member function can access data of that class.

d. Data Abstraction

Abstraction is representing essential features of an object without including the background details or explanation. In OOP, abstraction is achieved by the help of class, where data and function are combined to extract the essential features only.

e. Inheritance

Inheritance is the process by which one class acquires the characteristics or property of another class. Inheritance is the process of creating new classes from the existing classes. New class is called derived class and existing class is called base class.

Inheritance is the property that allows the reuse of an existing class to build a new class.

Types of Inheritance

1. Single Inheritance: Under this type of inheritance, there is a derived class with only one base class i.e., if a child class is built from only one parent class, then this type of inheritance is called single inheritance.
   For example:
   Parent class
   ↓
   Child class
2. Multi-level Inheritance (also written as multi inheritance): Under these types of inheritance, the derived class has several base classes. If a child class is built from two or more parent classes, then this type of inheritance is called multi-level inheritance.
   For example:
   parent-class 1

   parent-class 2

   parent-class 3
   ↓
   Child-class
3. Hierarchical Inheritance: Under this type of inheritance, the behaviour of one class may be derived by more than one class.
4. Multiple Inheritance: Under this type of inheritance, the mechanism of deriving a class from another derived class.

f. Polymorphism

The word polymorphism is derived from the Greek word 'poly' which means 'many' and 'morph' which means 'form'. Polymorphism means "having many forms." Polymorphism means that the same functions may behave differently in different classes. Example of polymorphism in OOP is operator overloading, function overloading.

3. Advantages of OOP

• System can be easily upgraded from small to large systems.
• Software complexity can be easily managed.
• New data and functions can be easily added whenever necessary.
• Code reusability is possible due to the feature of inheritance.
• The data hiding concept helps the programmer to create secure programs.

Disadvantages of OOP

• Use of OOP is wastage of time in the case of small projects.
• Object oriented programs are much larger than other programs.
• Object oriented programs are slower because of their size.
• Programmers have to think differently.
• It needs lots of testing procedures.