What Is a Class in Programming?

What a class is

In programming, a class is a blueprint or template for creating objects. It defines what data (properties) and actions (methods) a particular kind of object will have, without being an actual object itself. Think of a class as the architectural plan for a house: the plan describes what the house will be like, and you can build many actual houses from it. A class is central to object-oriented programming, which organizes software around classes and objects.

Classes and objects

The relationship between a class and an object is the heart of the idea. The class is the definition; an object is a concrete instance created from it. A 'Dog' class might specify that every dog has a name and a breed, and can bark. From that one class, you can create many individual dog objects, each with its own name and breed. The class is written once; the objects are the many actual things made from it.

What a class defines

A class specifies two things for its objects: their properties and their methods. The properties are the data each object will hold, for a 'BankAccount' class, perhaps an account number and a balance. The methods are the actions each object can perform, like deposit and withdraw. By defining these in one place, the class ensures every object of that type has the same structure and capabilities, while each object holds its own individual values.

Why use classes

Classes bring major benefits to organizing code. They let you define a type of thing once and create as many instances as you need, avoiding repetition. They keep related data and behavior together in a clear, reusable structure. And they make large programs easier to understand by organizing them around meaningful concepts, accounts, users, products, rather than loose piles of variables and functions. This organization is a big reason object-oriented programming became so widely used.

Classes and inheritance

Classes also enable 'inheritance,' a powerful feature where one class can be based on another, taking on its properties and methods and adding or changing some. For example, a general 'Vehicle' class could have specialized 'Car' and 'Truck' classes built from it. This lets programmers share common features and build hierarchies of related types, reducing duplication and reflecting real relationships between concepts. Inheritance is one of the key ideas that classes make possible.

Why it matters

Classes are a foundational concept in object-oriented programming, the blueprint from which objects are made. Understanding them, and how they relate to objects, clarifies how much of modern software is structured and how code models real-world concepts. For anyone learning to program beyond the basics, classes are an essential idea: they are the organizing principle behind a huge amount of the software written today.

Related on Skillo

See also: What is an object in programming?, What is inheritance in programming?.

Sources

• Class (computer programming) - Wikipedia

Published date reflects the original event date (2024-07-16). This article is original Skillo editorial written from the sources above; facts were verified in September 2026.