OOP from Zero to Advanced

Introduction

• Welcome to the college lecture.
• Today's focus: Cover OOP from zero to advanced level.
• Applicable for interviews (placements, internships) and college exams.
• Importance: Strong understanding of OOP for technical interviews, improving programming understanding, and its frequent implementation in companies.

Agenda

• Theory concepts
• Examples
• Important definitions
• Practical coding examples in C++
• 30 MCQ questions at the end of the session

Object-Oriented Programming (OOP) Overview

• What is OOP?
  • A better way to write code that’s reusable and reflects real-world entities.
  • Major OOP Concepts: Class and Object
• Class vs. Object
  • Class: Blueprint for objects. Defines properties (attributes) and methods (functions).
  • Object: Instance of a class with unique values.

Practical Example

1. Class Teacher
   • Properties: Name, Department, Subject, Salary
   • Methods: ChangeDepartment (to change the teacher's department)
   • Access modifier: Public and Private members

Access Modifiers

• Private: Accessible only within the class. (default)
• Public: Accessible from outside the class.
• Protected: Accessible within the class and derived classes.

Encapsulation

• Definition: Wrapping data and methods into a single unit (class).
• Implementation: Using access modifiers to ensure data hiding.
• Example: Teacher class with private properties and public methods.

Constructor

• Special method called automatically at the creation of an object.
• Types:
  • Default (Non-parameterized) Constructor
  • Parameterized Constructor
  • Copy Constructor: Copies properties from one object to another.
• Example:
  • Teacher class with multiple constructors demonstrating overloading.

Destructor

• Opposite of Constructor, called automatically when an object goes out of scope.
• Purpose: Free allocated memory.
• Destructor Example: ~Teacher() { // Cleanup code }

Inheritance

• Definition: Mechanism where one class inherits properties and behavior from another.
• **Types: **
  • Single Inheritance: One parent, one child
  • Multi-level Inheritance: Chain of classes
  • Hierarchical Inheritance: Multiple children, one parent
  • Multiple Inheritance: One child, multiple parents
• Access Modifiers Roles in Inheritance
• Practical Example:
  • Person, Student, and Teacher classes demonstrating different inheritance types.

Polymorphism

• Definition: Ability of different objects to respond uniquely to the same function.
• Types:
  • Compile-time Polymorphism: Function/Constructor overloading
  • Run-time Polymorphism: Function overriding, virtual functions
• Examples:
  • Function Overloading: Multiple functions with the same name but different parameters.
  • Function Overriding: Child class overrides the parent class function.

Abstract Class

• Definition: A class that cannot be instantiated. Meant for other classes to derive from.
• Uses: Provides a base for subclasses to enforce a contract.
• Pure Virtual Function: Implement with virtual keyword and =0 virtual void draw() = 0;
• Example: Abstract Shape class with Circle and Square derived classes.

Static Keyword

• Use with variables and methods.
• Static Variables: Retain value throughout the program.
  • Static Member Example: Shared by all instances of a class.
  static int count;
• Static Methods: Can be called on the class itself rather than instances.

Conclusion

• Review: Understanding key OOP concepts: Encapsulation, Inheritance, Polymorphism, Abstract Classes, Static Keyword.
• Preparation: Focus on theory but also enhance understanding through coding examples and solving MCQs.
• Practical Implementation: Keep practicing and reviewing key concepts for internships and placements.

All the best for your interviews and exams! Keep learning and keep hustling.