LESSON 275 OF 667 · FUNCTIONS & CLASSES

Defining a Class in C++

Lesson

TL ; DR:

A class is a blueprint for creating objects. It groups together related data and behavior under a single name.
In C++, you define a class with the class keyword, followed by the class name and a pair of curly braces. Don't forget the trailing semicolon:
```
class Dog {
};
```
The body of the class can be empty — that's still a valid class. We'll add data and behavior to it in the next lessons.

Full lesson:

So far, you've worked with built-in types like int, string, and arrays. But what if you want to model something the language doesn't have a type for — like a Dog, a BankAccount, or a Game?

That's what classes are for. A class lets you define your own type by listing what data it holds and what actions it can perform.

Why classes?

Imagine you're writing a program about dogs. Each dog has a name, an age, and can bark. Without classes, you'd have to track each dog's name in one variable, age in another, and write a separate bark() function for each. That gets messy fast.

With a class, you bundle all of that into one neat package called Dog:

class Dog {
    // We'll add member variables and methods in upcoming lessons.
};

The syntax

Defining an empty class in C++ looks like this:

class ClassName {
};

Three things to notice:

The keyword class tells C++ you're defining a new type.
ClassName is the name you choose. By convention, C++ class names use PascalCase — capitalized words with no underscores: Dog, BankAccount, HighScore.
The curly braces { } hold the body of the class, and a semicolon goes after the closing brace. This is a quirk of C++ — forget it and you'll get a confusing compiler error.

Your task

Define an empty class called Dog. The pre-filled code in mainFunction will create an instance of your class and print a confirmation message. If you define the class correctly, the program will compile and print:

Defined the Dog class!

STEP 1 OF 1

Guided

Ctrl + Enter to check