Lecture on Object-Oriented Programming (OOPs)

Introduction

• Objective: Cover OOPs from basic to advanced, focusing on interview preparation for placements and internships.
• Importance:
  • Major concept for tech interviews.
  • Strong understanding required for programming tasks in companies.

Key Topics to Cover

1. Theory concepts.
2. Practical examples.
3. Important definitions.
4. Code implementation for each concept.
5. 30 MCQ questions at the end.

Concepts of OOPs

Overview of OOPs

• Writing better organized code using objects and classes.
• Real-life scenarios often become easier to represent using OOPs.
• Example: C++'s vector, string, stack libraries use OOPs concepts internally.

Classes and Objects

Definitions

• Object: Real-world entities (e.g., a pen, laptop, phone).
• Class: Blueprint for objects, defining how objects should look (includes properties and methods).
  • E.g., for a teacher: properties could be name, department, subject, salary.

Example: Teacher System

• Class Definition: Class defines properties and methods for a teacher.
• Object Creation: Instantiate objects using the class blueprint.
  • Example code provided for C++ implementation.

Access Modifiers

• Private: Members are accessible only within the class.
• Public: Members are accessible from outside the class.
• Protected: Members are accessible within the class and by derived classes.

Example Code:

• Demonstration of using public, private, and protected access modifiers in C++.
• Example scenario: Printing and modifying teacher details using access modifiers.

Encapsulation

• Definition: Wrapping data and member functions into a single unit (class).
• Data Hiding: Protecting sensitive information using private and protected access modifiers.
• Getter/Setter Methods: Used to access private variables indirectly.
  • Example code: Using getter and setter methods for Teacher's salary.

Constructors and Destructors

Constructors

• Purpose: Initialize objects of a class.
• Types: Default, Parameterized, Copy Constructors.
• Practical Example: Using constructors to initialize teacher details.
• This Pointer: Points to the calling object.
• Shallow vs. Deep Copy: Difference and issues explained with examples.

Destructors

• Purpose: Deallocate memory used by objects.
• Destructor Example: Automatic call vs. explicit destructor implementation in C++.
• Dynamic Memory Deallocation: Using delete keyword.

Inheritance

• Definition: Derived class inherits properties and methods from the base class.
• Importance: For code reuse.
• Key Points:
  • Base Class and Derived Class: Naming conventions and examples.
  • Constructor and Destructor Calls: Order of execution during inheritance.
  • Inheritance Modes: Public, Protected, Private with detailed examples.
  • Types of Inheritance: Single, Multilevel, Multiple, Hierarchical, Hybrid.
  • Practical Examples: Scenarios demonstrating various inheritance types.

Polymorphism

• Definition: Ability of objects to take on different forms.
• Types: Compile-time (static) and runtime (dynamic) polymorphism.
• Examples:
  • Constructor Overloading: Different constructors for different initializations.
  • Function Overloading: Same function name with different parameters.
  • Function Overriding: Derived class overrides base class methods.
  • Virtual Functions: Functions expected to be overridden in derived classes.

Abstraction

• Definition: Hiding unnecessary details and showing only essential features.
• Implementation:
  • Access Modifiers: Using public, private, protected.
  • Abstract Classes: Classes with at least one pure virtual function.
  • Example: Shape class with derived classes like Circle and Square.

Static Keyword

• Usage: Can be applied to members of a class to share them among all instances.
• Static Variables:
  • Remain persistent for the lifetime of the program.
  • Example: Shared counter across multiple objects.
• Static Functions: Can be called without object instantiation.
• Example: Demonstrates static variable behavior across function calls and objects.

Conclusion

• Comprehensive coverage of OOPs concepts with practical coding examples.
• Importance of understanding and applying OOPs principles in interviews and practical programming.
• Encouragement to further self-study and explore advanced topics like friend functions and classes.

Final Notes

• Remember definitions and examples for key concepts as they are frequently asked in interviews.
• Solve the provided 30 MCQ questions for better understanding and practice.