OOPs Concepts: Zero to Advanced

Introduction

• Welcome to the session focused on OOPs (Object-Oriented Programming)
• Target audience: Students preparing for internships, placements, or college exams in OOPs.
• Importance of OOPs for tech interviews and strong programming foundation.

Key Topics Covered

• Theory concepts
• Examples and code in C++
• Important definitions and MCQ questions at the end

Object-Oriented Programming (OOPs)

• What is OOPs?
  • Better way to write code, not always necessary but makes code better and more organized.
  • Real-life usefulness in object representation in code.

Basic Terms in OOPs

• Class: Blueprint of objects.
• Object: Instance of a class, representing real-world entities.

Core Concepts in OOPs

1. Class and Object

   • Example: Teacher class
     • Properties: name, department, subject, salary
     • Methods (member functions): change department, etc.
   • Code Example
   class Teacher { public: string name; string department; string subject; double salary; void changeDepartment(string newDept) { department = newDept; } };
   • Create objects: Teacher t1;

2. Access Modifiers

   • Types: private, public, protected
   • Controls access to class members
   • Code Example
   class Teacher { private: double salary; public: string name; string department; string subject; }

3. Encapsulation

   • Wrapping data and methods into a single unit (class).
   • Hides sensitive information using private members.

4. Constructor and Destructor

   • Constructor: Special function called auto when an object is created. Used for initialization.
   • Destructor: Special function called auto when an object is destroyed. Used for cleanup.
   • Types: Default, Parameterized, Copy
   • Code Example
   class Teacher { public: Teacher() { cout << "Hi, I am a constructor"; } Teacher(string n): name(n) { cout << "Parameterized constructor"; } ~Teacher() { cout << "Destructor called"; } };

5. Inheritance

   • Deriving new class from existing class.
   • Types: Single, Multilevel, Multiple, Hierarchical, Hybrid
   • Base class (Parent class) and Derived class (Child class)
   • Code Example
   class Person { public: string name; int age; }; class Student : public Person { public: int rollNumber; };
   • Constructor Order: Base class constructor first, then derived class constructor
   • Destructor Order: Derived class destructor first, then base class destructor

6. Polymorphism

   • Ability to take multiple forms. Two types: Compile-time and Run-time.
   • Compile-time Polymorphism: Function overloading, Constructor overloading
   • Run-time Polymorphism: Function overriding, Virtual functions
   • Code Example
   class Parent { public: virtual void show() { cout << "Parent"; } }; class Child : public Parent { public: void show() override { cout << "Child"; } };

7. Abstract Classes

   • Base class with at least one pure virtual function.
   • Cannot instantiate objects; used for inheritances
   • Code Example
   class Shape { public: virtual void draw() = 0; // Pure virtual function }; class Circle : public Shape { public: void draw() override { cout << "Drawing Circle"; } };

8. Static Members

   • Shared among all instances of a class.
   • Static variables/functions persist for the lifetime of the program.
   • Code Example
   class MyClass { public: static int count; MyClass() { count++; } }; int MyClass::count = 0;

9. Miscellaneous Concepts

   • Friend Function and Friend Class (Explore further as homework)
   • Inter-class interactions
   • Best practices in OOPs

Practice and Revision

• Solve MCQ questions related to OOPs concepts.
• Make notes and remember definitions.
• Apply examples in practical coding scenarios.

Conclusion

• Review key concepts.
• Prepare for interviews by deeply understanding and applying OOPs concepts.
• Best of luck for internships and placements.