In C++, a class is a user-defined data type that serves as a blueprint for creating objects. Classes group data (attributes) and functions (methods) into a single unit, supporting encapsulation, one of the fundamental principles of Object-Oriented Programming (OOP).

What is a Class?

A class defines the properties and behaviors that its objects will have. It consists of:

1. Attributes (Data Members):
   • Represent the properties or characteristics of the class.
   • Declared as variables within the class.
2. Methods (Member Functions):
   • Define the actions or behaviors of the class.
   • Operate on the data members.

Key Components of a Class

1. Access Modifiers:
   • Control the accessibility of class members.
   • Private: Accessible only within the class.
   • Public: Accessible from outside the class.
   • Protected: Accessible within the class and derived classes.
2. Constructor:
   • A special function that initializes objects of the class.
   • Automatically called when an object is created.
3. Member Functions:
   • Functions defined inside the class to operate on the data members.

Example Code: Car Class

Below is an example of a Car class in C++ that demonstrates its components.

Class Code:

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

class Car {
//Creating attributes of the Class
private:
    int price;
    string color;

public:
    string name;
    // Constructor to initialize the attributes
    Car(int p, string n, string c) {
        price = p;
        name = n;
        color = c;
    }
    // Creating Methods of the class
    void show() {
        cout << "The Name of Car is: " << name << endl;
        cout << "The Color of the Car is: " << color << endl;
        cout << "The Price of the Car is: " << price << " PKR" << endl;
    }
    void start() {
        cout << "The Car Starts" << endl;
    }
    void stop() {
        cout << "The Car Stops" << endl;
    }
    void accelerate() {
        cout << "The Car Accelerates" << endl;
    }
};

Explanation of the Class Code:

1. Attributes:
   • price and color are private attributes, accessible only within the class.
   • name is a public attribute, accessible outside the class.
2. Constructor (Car):
   • Initializes the car’s price, name, and color when an object is created.
3. Member Functions:
   • show: Displays the car’s details.
   • start, stop, accelerate: Represent actions that the car can perform.

Main Function Code:

int main() {
    // Creating an object of the Car class
    Car c1(1500000, "Civic", "Black");

    // Calling the Car functions
    c1.show();
    c1.start();
    c1.stop();
    c1.accelerate();

    return 0;
}

Explanation of the Main Function:

1. Object Creation:
   • Car c1(1500000, "Civic", "Black") creates an object c1 of the Car class.
   • The constructor initializes c1 with:
     • Price: 1500000
     • Name: “Civic”
     • Color: “Black”
2. Calling Member Functions:
   • c1.show() displays the car’s details.
   • c1.start(), c1.stop(), and c1.accelerate() simulate the car’s actions.

Output of the Program:

The Name of Car is: Civic
The Color of the Car is: Black
The Price of the Car is: 1500000 PKR
The Car Starts
The Car Stops
The Car Accelerates

Benefits of Using Classes in C++:

1. Encapsulation:
   • Combines data and functions into a single unit.
   • Restricts direct access to private members.
2. Reusability:
   • Once defined, the class can be reused to create multiple objects.
3. Modularity:
   • Code is organized, making it easier to manage and debug.

Conclusion:

Classes are the foundation of Object-Oriented Programming in C++. By combining attributes and methods, they enable programmers to model real-world entities effectively. In this example, the Car class encapsulates details about a car and provides actions (methods) that mimic its behavior, demonstrating the utility of classes in C++.