Introduction to OOP in C++

Object-Oriented Programming (OOP) is a programming style that organizes code around objects — real-world entities — rather than just functions and logic. C++ is a multi-paradigm language that fully supports OOP, and it is one of the most important aspects of C++ programming.

What is OOP?

In the real world, everything is an object — a car, a bank account, a student. Each object has:

• Properties (Attributes) — What the object has. A car has a color, engine, and speed.
• Behaviors (Methods) — What the object does. A car can accelerate, brake, and turn.

OOP models software the same way — classes define the blueprint, and objects are the real instances created from that blueprint.

Four Pillars of OOP

Procedural vs Object-Oriented Approach

Procedural approach (no OOP):

// All data and logic are separate
string studentName = "Asha";
int studentAge = 20;

void printStudent(string name, int age) {
    cout << name << " - " << age << endl;
}

Object-Oriented approach:

class Student {
public:
    string name;
    int age;

    void print() {
        cout << name << " - " << age << endl;
    }
};

In OOP, related data and functions are grouped inside a class. This leads to cleaner, more maintainable, and reusable code.

Class and Object — Quick Preview

A class is a blueprint. An object is an instance of that class — a real working entity.

#include <iostream>
#include <string>
using namespace std;

class Car {
public:
    string brand;
    int speed;

    void showInfo() {
        cout << brand << " runs at " << speed << " km/h" << endl;
    }
};

int main() {
    Car car1;          // create an object
    car1.brand = "Toyota";
    car1.speed = 180;
    car1.showInfo();   // use the object

    Car car2;
    car2.brand = "BMW";
    car2.speed = 250;
    car2.showInfo();

    return 0;
}

Output:

Toyota runs at 180 km/h
BMW runs at 250 km/h

Benefits of OOP

• Modularity — Code is divided into classes, each handling its own responsibility.
• Reusability — Existing classes can be extended and reused without rewriting.
• Maintainability — Changes in one class don't break unrelated parts of the program.
• Security — Encapsulation hides sensitive data from outside access.
• Real-world modeling — OOP naturally maps to how we think about the world.

Real-World OOP Examples

Key Takeaways

• OOP organizes code around objects that represent real-world entities.
• A class is a blueprint; an object is a concrete instance of it.
• The four pillars of OOP are: Encapsulation, Inheritance, Polymorphism, and Abstraction.
• OOP makes code more organized, reusable, and maintainable.
• C++ fully supports OOP alongside procedural programming.