Object-Oriented Programming



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Object-Oriented Programming :

  • OOP is the methodology to create a program using classes and objects.
  • A class is a blueprint of an object.
  • Objects are the basic unit of OOP.
  • OOP associated with the concept like Class, Object, Inheritance, Abstraction, Encapsulation, Polymorphism.
  • It improves software development productivity by providing Modularity, Reusability and Extensibility.
  • Reusability enables the faster development and lower the price of development.
  • OOP is larger in size and slower is speed.
  • OOP provide ability to simulate the real-world events easily.
  • It is easy to maintenance.

 

Advantages –

  • Data security
  • Inheritance
  • Code reusability
  • Flexible and Abstraction is also present.

 

Applications –

  • It simplify a complex problem in a real-busines system.
  • Hundreds of windowing systems have been developed using OOP techniques.
  • OOP has enabled the software industry to improve the quality of software system and also its productivity.
  • Object-oriented technology is certainly changing the way of software engineers think, analyze, design and implement systems.

 

Procedural-Oriented Programming :

  • POP is a type of computer programming language that follows the step-by-step approach and procedures to execute methods and functions.
  • It follows Up-Down approach.
  • It separates the program within variable, functions, statements and conditional operators.
  • Focus of procedural programming is to break down the program into variables, data structures and subroutines.

          e.g- C, BASIC, FORTRAN, PASCAL etc.

 

Advantages –

  • POP is simple to implement.
  • It needs very less memory.
  • An easy way to keep track of program flow.
  • Global data can be accessed from anywhere in the program.

 

Disadvantages –

  • In POP, data is less secure.
  • No data hiding mechanism.
  • Difficult to relate with real-world objects.
  • Complex problem cannot be solved.
  • Overloading is not possible.
  • It does not have any access specifier.
  • It is less efficient and less productive.

 

Difference between Procedural-Oriented Programming (POP) and Object-Oriented Programming (OOP) :

 

POP

OOP

1.

It follows step-by step approach to execute a function and methods.

Various functions can work simultaneously.

2.

It follows Top-Down approach.

It follows Bottom-Up approach.

3.

It is less secure.

It is more secure than POP.

4.

It needs very less memory.

It needs more memory than POP.

5.

Programs are divided into functions.

Programs are divided into objects.

6.

It deals with algorithm.

It deals with data.

7.

It doesn’t have any access specifier.

It has access specifier like Private, Public & Protected.

8.

Overloading is not possible in POP.

Overloading is possible in the form of Function Overloading and Operator Overloading.

9.

There is no data hiding mechanism.

It is possible to hide data.

10.

Function communicates with each other by passing parameters.

Object communicate with each other by passing message.

 

Object in OOP :

  • Object is a real-word entity.
  • It has states(data) and behaviour(functionality).
  • Object is a runtime entity which is created at runtime.
  • Object is an instance of a class. All the members of class can be accessed through objects.

 

Class in OOP :

  • A Class is a group of similar objects.
  • It is a blueprint or template form which objects are created.
  • It represents the set of properties that are common to all the objects of one type.
  • A class specification has two parts-

          1) Private

          2) Public

  • Private data can be accessed only within the Class.
  • Public data can be accessed from outside the Class.
  • The Keyword ‘Private’ is optional. By default, Class Members are private.
  • Each part has two types of elements-

          1) Data Member

          2) Member Function

  • The Variables (data member) and Functions (member function) are collectively known as Class Member.  
  • General form of Class declaration-

class class_name

{

   Private:

      Data member;

      Member function;

   Public:

      Data member;

      Member function;

};

 


Create an Object in OOP :

  • Create an object of a class like a variable creation of some basic data type.
  • Object is created in two places of program-

       (1) In class immediately after the closing curly bracket.

         

class book

{

  Body of book;

} b1, b2, b3 ;    // declaration of objects


       (2) In main program.

    

class book

{

  Body of book;

};

  int main()

{

  book b1, b2, b3 ;   // objects of class book

}

 

 

Constructor :

  • It is a member function of class.
  • It is always present in Public section of class.
  • It has same name as that of class.
  • It is called automatically when an object of the class is created.
  • It is not returning any value (no return type) even void also.
  • It reserves memory.
  • Constructor is declared as-

class student

{

  private:

    int roll;

    char name[10];

  public:

    student();       // Constructor declaration

};

 


Features of Constructor –

  1. Constructor is always declared in the Public section.
  2. It is called automatically when an object of the class is created.
  3. It has no return type not even void.
  4. It cannot be inherited and virtual.

 

Destructor :

  • It is a member function of class.
  • It is always present in Public section of class.
  • It has same name as that of class but followed by a special symbol ~ (tilde).
  • It is called automatically when an object of the class is destroyed.
  • It is not returning any value (no return type) even void also. It takes no argument.
  • It destroys memory when called.
  • Constructor is declared as-

class student

{

 private:

    int roll;

    char name[10];

  public:

    ~student();       // Destructor declaration

};

 

 

Features of Destructor –

  1. Compiler itself called the Destructor when an object is destroyed.
  2. It has no return type even void.
  3. It cannot be inherited and virtual.
  4. It is de-locate the memory that was allocated by Constructor for the Object.

 

Difference between Constructure and Destructure :

Constructure

Destructure

A constructor is called when a new instance of a class is created.

Destructor called when an already existing instance of a class is destroyed.

Its name is same as class name.

Its name is same as class name but it preceded by tilde (~).

It can take arguments.

It doesn’t take any argument.

It can be overloaded.

It can’t be overloaded.

Multiple constructors can coexist inside the class

Only one destructor exists in a class.

It is called each time a class is instantiated.

It is called automatically when an object is detected from memory.

e.g – student (int a, int b)

e.g – ~student ()

 

 







Handwritten pdf Note-1 download

Handwritten pdf Note-2 download

OPP Book (E. Balagurusamy) download