Mastering C++: From Fundamentals to Advanced Programming

Chapter 6: Object-Oriented Programming (OOP) in C++

🔹 1. Introduction

Object-Oriented Programming (OOP) is a programming paradigm based on the concept of "objects", which contain both data (attributes) and functions (methods). C++ was one of the first mainstream languages to implement OOP, and it remains one of the most powerful tools for modular, scalable, and reusable software design.

🔹 2. Core Principles of OOP

🔹 3. Classes and Objects

✅ Class: Blueprint for creating objects

class Car {

public:

    string brand;

    void honk() {

        cout << "Beep Beep!";

    }

};

✅ Object: Instance of a class

int main() {

    Car myCar;

    myCar.brand = "Toyota";

    myCar.honk(); // Output: Beep Beep!

}

🔹 4. Access Specifiers

🔹 5. Constructors & Destructors

✅ Constructor: Initializes object automatically

class Person {

public:

    string name;

    Person(string n) {

        name = n;

    }

};

✅ Destructor: Cleans up when object is destroyed

~Person() {

    cout << "Object destroyed";

}

🔹 6. Inheritance in C++

Inheritance allows one class to derive features from another.

✅ Example:

class Animal {

public:

    void sound() {

        cout << "Animal sound\n";

    }

};

class Dog : public Animal {

public:

    void bark() {

        cout << "Dog barks\n";

    }

};

✅ Use:

Dog d;

d.sound();  // Inherited

d.bark();   // Own method

🔹 7. Types of Inheritance

🔹 8. Polymorphism

✅ Function Overloading (Compile-Time Polymorphism)

class Math {

public:

    int add(int a, int b) {

        return a + b;

    }

    float add(float a, float b) {

        return a + b;

    }

};

✅ Function Overriding (Run-Time Polymorphism)

class Base {

public:

    virtual void greet() {

        cout << "Hello from Base\n";

    }

};

class Derived : public Base {

public:

    void greet() override {

        cout << "Hello from Derived\n";

    }

};

✅ Virtual Functions

Allow dynamic dispatch during runtime (used with base class pointers).

🔹 9. Encapsulation and Abstraction

Encapsulation is the practice of keeping variables private and accessing them via public methods.

class Account {

private:

    int balance;

public:

    void deposit(int amount) {

        balance += amount;

    }

    int getBalance() {

        return balance;

    }

};

✅ This protects internal details and exposes only what's necessary (abstraction).

🔹 10. Real-World Example: Student Management

class Student {

private:

    string name;

    int rollNo;

public:

    Student(string n, int r) {

        name = n;

        rollNo = r;

    }

    void display() {

        cout << "Name: " << name << ", Roll No: " << rollNo;

    }

};

🔹 Summary Table