C++ Classes & Objects
Understanding object-oriented programming fundamentals
🏗️ What are Classes & Objects?
Classes are blueprints for creating objects in C++. Objects are instances of classes that contain data (attributes) and functions (methods) to work with that data.
// Simple class example
class Car {
public:
string brand;
string model;
int year;
};
// Creating an object
Car myCar;
myCar.brand = "Toyota";
Output:
Car object created with brand: Toyota
Key OOP Concepts
Class
Blueprint or template for objects
class Student {
string name;
int age;
};Object
Instance of a class
Student student1;
Student student2;Attributes
Data members of a class
class Person {
string name;
int age;
};Methods
Functions inside a class
class Calculator {
int add(int a, int b) {
return a + b;
}
};🔹 Creating Your First Class
A simple class like Dog introduces core object-oriented concepts: attributes and
methods. Attributes (e.g., name, breed, age) define state, while methods (e.g., bark(),
displayInfo()) define behavior. This foundational exercise teaches encapsulation by bundling related
data and functions into a single, reusable unit, forming the basis for more complex software design.
#include <iostream>
#include <string>
using namespace std;
class Dog {
public:
// Attributes
string name;
string breed;
int age;
// Method
void bark() {
cout << name << " says Woof!" << endl;
}
void displayInfo() {
cout << "Name: " << name << endl;
cout << "Breed: " << breed << endl;
cout << "Age: " << age << " years" << endl;
}
};Class Structure:
Dog class with attributes: name, breed, age
Methods: bark(), displayInfo()
🔹 Creating and Using Objects
Objects are instances of a class, created to use the defined blueprint in a program. For example,
from a Dog class, you can instantiate objects like buddy and max, each with
unique attribute values. Interacting with these objects through their methods brings the class to life,
demonstrating how object-oriented programming models real-world entities and interactions.
int main() {
// Create objects
Dog dog1;
Dog dog2;
// Set attributes for dog1
dog1.name = "Buddy";
dog1.breed = "Golden Retriever";
dog1.age = 3;
// Set attributes for dog2
dog2.name = "Max";
dog2.breed = "German Shepherd";
dog2.age = 5;
// Use methods
dog1.displayInfo();
dog1.bark();
cout << endl;
dog2.displayInfo();
dog2.bark();
return 0;
}Output:
Name: Buddy
Breed: Golden Retriever
Age: 3 years
Buddy says Woof!
Name: Max
Breed: German Shepherd
Age: 5 years
Max says Woof!
🔹 Complete Example
A self-contained example, such as a Rectangle class, showcases a class in its entirety.
It includes attributes (length, width), a constructor for initialization, and methods to calculate area and
perimeter. This complete picture illustrates how classes encapsulate data and operations, providing a template for
creating multiple, independent objects that share common behavior.
#include <iostream>
#include <string>
using namespace std;
class Rectangle {
public:
double width;
double height;
double calculateArea() {
return width * height;
}
double calculatePerimeter() {
return 2 * (width + height);
}
void displayInfo() {
cout << "Rectangle: " << width << " x " << height << endl;
cout << "Area: " << calculateArea() << endl;
cout << "Perimeter: " << calculatePerimeter() << endl;
}
};
int main() {
Rectangle rect;
rect.width = 5.0;
rect.height = 3.0;
rect.displayInfo();
return 0;
}Output:
Rectangle: 5 x 3
Area: 15
Perimeter: 16