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Notes of Object Oriented Programming [CT 501]

Introduction to Object Oriented Programming

Issues with Procedural Programming

- In procedure oriented approach, the problem is analyzed and as a sequence of things to be done like reading, calculating and displaying for which functions are used.
- Some common POP programming languages are COBOL, C, FORTRAN and so on.

Characteristics of POP

1. Emphasis is on algorithms
2. Follows top to bottom approach
3. Coding of large program is done by dividing it into smaller modules called functions
4. Global data can be shared by any functions
5. Functions are capable of transferring data from one form to another

Limitations of POP

1. Functions are emphasized rather than data.
2. Global data are vulnerable to an inadvertent change by a functions
3. Difficulty in recognizing which function uses which global data
4. Modification in global data also requires modification in functions using it
5. Function are action oriented so can not correspond to elements of the problem. So, it does not model the real world problems.

Basic OOP

- In other to solve the limitations of the POP, the concept of OOP arises.
- In OOP, emphasis is given to data because of which data are protected from being accidental modification or data corruption.
- Large problem is divided into objects and then build data and function around them.

Features of OOP

1. Emphasis is given on data rather than procedures.
2. Programs are divided into objects.
3. Function and data are tied together in a single unit.
4. Data can be hidden to prevent from accidental alteration from other functions.
5. Data access is done through the visible function.
6. Objects can communicate with each other through functions.
7. Follows bottom up approach.

Procedure Oriented vs Object Oriented Programming


Procedure oriented Object oriented
  1. Emphasis is given on procedure.
  2. Programs are divided into functions.
  3. Data can not be hidden.
  4. It does not model the real world problems.
  5. Data moves from function to function.
  6. Maintaining and enhancing code is still difficult.
  7. Code reusability is difficult.
  8. Follows top-down approach.
  9. Eg: COBOL, C
  1. Emphasis is given on data.
  2. Programs are divided into objects.
  3. Data can be hidden.
  4. It models the real world problems.
  5. Data and function are tied together.
  6. Maintaining and enhancing code is easy.
  7. Code reusability is easy.
  8. Follows bottom-up approach.
  9. Eg: JAVA, C++


Concept of Object Oriented Programming

1. Object:

- Objects are the basic run time entities in an object oriented system.
- They represent any item that the program can handle.
- The objects are so chosen to match with the real world objects.
- When a program is executed, the objects interact by sending messages to one another.
- Eg: Consider an object ‘student’ with data (name, roll, mark) and functions {total(), average(), display()}

2. Class:

- Class is the user defined data type used to declare the object.
- It is possible to declare any number of objects belonging to that class.
- Each object of a class is associated with the data of that class.
- Eg: To create an object mango belonging to the class fruit;
fruit mango;

3. Abstraction:

- Abstraction is the act of representing the essential features without including the background details or explanations.
- Classes are the concept of abstraction. So, class is a abstract data type.
- It can manage the program complexity.

4. Encapsulation:

- Encapsulation is the mechanism of combining data function together into a single unit.
- It prevents the data being accessed by other code.

5. Inheritance:

- Inheritance is the process of creating new classes based on the existing class such that new class acquires features from the existing class and adds more features on it.
- The process of deriving a new class from the existing base class is called inheritance.

6. Polymorphism:

- Polymorphism is the ability to take more than one form depending on what they are operating on.
- It allows different objects to respond to the same operation in different ways, the response being specific to the type of object.
- Eg: operator overloading, function overloading and so on.

Example of Some Object Oriented Languages

1. Small talk
2. Eiffel
4. C#
5. D
6. C++

Advantages and Disadvantages of OOP

Advantages of OOP

1. Data hiding ensures program security.
2. Software development becomes easy as programs are divided into objects.
3. Proper management of software complexity.
4. Ensure real world problems modeling.
5. Easy to reuse codes.
6. Techniques like inheritance and templates eliminates redundant code.

Disadvantages of OOP

1. Requires more compilation time.
2. Difficult to trace and debug errors in complex program.
3. No benefits in short run of programs.



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