Object-Oriented Programming in C++ – Classes, Inheritance, Polymorphism Explained

Object-Oriented Programming (OOP) is the heart of C++. It allows programmers to model real-world problems using classes and objects. Understanding OOP is very important for software development and technical interviews.

What is Object-Oriented Programming?

OOP is a programming paradigm that organizes code into reusable objects. Each object represents a real-world entity and contains data (variables) and behavior (functions).

1. Classes and Objects in C++

A class is a blueprint, and an object is its instance.

class Car {
public:
    string brand;
    int speed;

    void show() {
        cout << brand << " " << speed;
    }
};

int main() {
    Car c1;
    c1.brand = "BMW";
    c1.speed = 200;
    c1.show();
}

2. Encapsulation

Encapsulation means wrapping data and methods together and protecting them using access specifiers.

class Student {
private:
    int marks;
public:
    void setMarks(int m) {
        marks = m;
    }
    int getMarks() {
        return marks;
    }
};

3. Inheritance

Inheritance allows one class to acquire properties of another class.

class Animal {
public:
    void sound() {
        cout << "Animal makes sound";
    }
};

class Dog : public Animal {
public:
    void bark() {
        cout << "Dog barks";
    }
};

4. Polymorphism

Polymorphism means one function behaving differently in different situations.

class Shape {
public:
    virtual void draw() {
        cout << "Drawing Shape";
    }
};

class Circle : public Shape {
public:
    void draw() {
        cout << "Drawing Circle";
    }
};

5. Abstraction

Abstraction hides implementation details and shows only essential features.

class Vehicle {
public:
    virtual void start() = 0; // Pure virtual function
};

6. Constructor and Destructor

Constructors initialize objects and destructors free resources.

class Test {
public:
    Test() {
        cout << "Constructor called";
    }
    ~Test() {
        cout << "Destructor called";
    }
};

Common OOP Interview Questions

• Difference between class and object
• What is virtual function?
• What is runtime polymorphism?
• Explain abstract class and interface

Conclusion

OOP in C++ makes programs modular, reusable, and easier to maintain. Mastering classes, inheritance, and polymorphism will help you write professional-level software and crack interviews.

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