C++ OOP

What is OOP?

Object-Oriented Programming is a style of coding that organizes software into objects. An object groups together related data (called attributes) and the actions that work on that data (called methods). This mirrors how we think about things in the real world, such as a car that has a color and can drive.

Procedural programming, the older style, focuses on writing functions that act on separate data. OOP instead keeps the data and the functions that use it together, which often makes larger programs easier to organize, reuse, and maintain.

Classes and Objects

A class is a blueprint that describes what an object will look like. An object is a concrete thing created from that blueprint. Think of the class as the plan for a house and each object as an actual house built from that plan.

#include <iostream>
using namespace std;

class Dog {
public:
  string name; // attribute
  void bark() { // method
    cout << name << " says Woof!" << endl;
  }
};

int main() {
  Dog myDog;        // create an object
  myDog.name = "Rex";
  myDog.bark();     // Rex says Woof!
  return 0;
}

The Four Pillars of OOP

OOP is built on four main ideas. You will explore each one in later lessons, but here is a quick overview so you know where you are headed.

• Encapsulation: keeping data safe inside an object and controlling access to it.
• Inheritance: creating new classes based on existing ones to reuse code.
• Polymorphism: letting one action behave differently depending on the object.
• Abstraction: hiding complex details and showing only what matters.

#include <iostream>
using namespace std;

class Circle {
public:
  double radius;
  double area() {
    return 3.14159 * radius * radius;
  }
};

int main() {
  Circle small, big;
  small.radius = 2.0;
  big.radius = 5.0;
  cout << "Small area: " << small.area() << endl;
  cout << "Big area: " << big.area() << endl;
  return 0;
}