Object-Oriented Programming in C++

Imagine organizing a school science fair. Each project booth has students, a project name, a category, and a score. You wouldn’t store this information separately, instead, you think of each booth as one object with all its details grouped together.

C++ lets you organize programs the same way using classes and objects.
A class is like the blueprint of a booth, and an object is the actual booth created from it.

Today, you’ll teach your program to create real-world models the way humans naturally think.

Digital Student Profile

You’ll create a class Student that stores:

• Name
• Age
• Grade

Then create an object from this class and print a formatted profile:

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========================
   STUDENT PROFILE
   Name: Ali Khan
   Age: 15
   Grade: A
========================

This is your first step into object-oriented programming (OOP).

What Is a Class?

A class is a blueprint that defines what data an object will have and what it can do. Think of it like a template for creating many similar objects. It tells C++: “Any student will have these properties.”

Example

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class Student {
public:
    string name;
    int age;
};

What Is an Object?

An object is a real instance created from a class. It receives its own values for the properties defined in the class. Different objects can store different information.

Example

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Student s1;
s1.name = "Ali";

Member Variables

These are the attributes inside a class (like name, age, grade). Objects use these variables to store their own data. Every object keeps its data separate from others.

Member Functions

Functions inside a class define what an object can do. They help process or display the data stored inside an object. They make the object self-contained and capable.

Example

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void display() { cout << name; }

Constructors

A constructor is a special function that initializes an object when it’s created. It sets default or starting values automatically. This saves time and prevents uninitialized data.

Example

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Student() { age = 0; }

Access Modifiers

public means accessible from outside the class. private hides data inside the class and protects it. This is the foundation of encapsulation.

Let’s Build the Student Profile Program

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#include <iostream>
using namespace std;

class Student {
public:
    string name;
    int age;
    char grade;

    void display() {
        cout << "========================" << endl;
        cout << "   STUDENT PROFILE" << endl;
        cout << "   Name: " << name << endl;
        cout << "   Age: " << age << endl;
        cout << "   Grade: " << grade << endl;
        cout << "========================" << endl;
    }
};

int main() {
    Student s;

    s.name = "Ali Khan";
    s.age = 15;
    s.grade = 'A';

    s.display();

    return 0;
}

How It Works (2–3 lines)

• The class defines what data a student object holds.
• The object s stores actual values for that student.
• The display() function prints the formatted profile.

Test this instantly in the DevsCall AI Code Runner.

Learn Together with AI

Try prompts like:

• “Create a class named Car with brand, model, and year.”
• “Add a constructor to initialize values automatically.”
• “Explain public vs private in simple words.”
• “Write a class with a function that calculates total marks.”

AI can generate new examples or explain anything you’re unsure about.

Practice Time

Write a C++ program that:

• Creates a class Book with:
  • title
  • author
  • price
• Adds a display() function inside the class.
• Creates an object and prints:

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========================
   BOOK DETAILS
   Title: The Alchemist
   Author: Paulo Coelho
   Price: 1200
========================

Ask AI:

“How do I create multiple objects from the same class in C++?”