Introduction to Object-Oriented Concepts

Vaibhav • September 11, 2025

So far, we’ve been writing simple programs using just one class-Program-and one method-Main. That’s a great place to start. But as your programs grow, you’ll need a better way to organize your code. That’s where object-oriented programming (OOP) comes in.

In this article, we’ll introduce the core ideas behind object-oriented programming in C#. We won’t go deep yet-that’s coming in future chapters. For now, we’ll focus on what objects and classes are, why they matter, and how they’ll help you write better programs as you move forward.

What Is Object-Oriented Programming?

Object-oriented programming is a way of thinking about code. Instead of writing one long list of instructions, you group related data and behavior together into objects. These objects are based on classes, which act like blueprints.

You’ve already seen a class in action:

class Program
{
    static void Main(string[] args)
    {
        Console.WriteLine("Hello, world!");
    }
}

This is a class named Program. It contains a method called Main. So far, we’ve only used one class and one method, but in real-world programs, you’ll often have many classes-each representing a different kind of object in your application.

What Is a Class?

A class is a container for related data and behavior. It defines what an object can do and what information it holds. You can think of it as a template or blueprint.

For example, imagine you’re writing a program about books. You might define a class like this:

// Just a preview - we’ll explain this in detail later
class Book
{
    string title;
    string author;

    void DisplayInfo()
    {
        Console.WriteLine(title + " by " + author);
    }
}

This class describes what a book is: it has a title and an author, and it can display its information. You’re not creating any books yet-you’re just describing what a book should look like in code.

What Is an Object?

An object is a specific instance of a class. If a class is a blueprint, an object is the actual thing built from that blueprint.

Continuing with the book example, you might create an object like this:

// Also a preview - don’t worry about syntax yet
Book myBook = new Book();

This line creates a new Book object called myBook. You can then set its title and author, and call its methods. We’ll learn exactly how to do that in future chapters.

Why Use Objects?

As your programs grow, you’ll need a way to manage complexity. Object-oriented programming helps you do that by:

• Grouping related data and behavior together
• Making code easier to reuse and maintain
• Allowing you to model real-world things in your code

For example, if you’re building a game, you might have classes like Player, Enemy, and Weapon. Each class would define what that object is and what it can do. This makes your code more organized and easier to understand.

Objects You’ve Already Used

Even though you haven’t created your own objects yet, you’ve already used some. For example:

Console.WriteLine("Hello!");

Here, Console is a class provided by the .NET framework. It has a method called WriteLine that prints text to the screen. You’re calling a method on a class-just like you’ll do with your own classes later.

Another example:

string name = Console.ReadLine();

Here, name is a variable of type string. The string type is actually a class too! When you use name.Length or name.ToUpper(), you’re calling methods on a string object.

What’s Coming Next

In future chapters, we’ll dive deeper into object-oriented programming. You’ll learn how to:

• Define your own classes
• Create and use objects
• Group related code into reusable components
• Use concepts like inheritance and encapsulation

For now, just remember that object-oriented programming is about organizing your code around real-world things. You’ve already seen classes and methods. Soon, you’ll be writing your own.

Summary

In this article, you got your first look at object-oriented programming in C#. You now understand:

• What classes and objects are
• How classes act as blueprints for objects
• Why object-oriented programming helps organize code
• That you’ve already been using objects like Console and string

This is just the beginning. In future chapters, you’ll learn how to create your own classes and build programs that are more powerful, more organized, and easier to maintain. But for now, you’ve taken the first step into the world of object-oriented programming.