Can the use of classes be considered a main feature of object-oriented programming?

Using classes is an important aspect of object-oriented programming (OOP), but not the only or main characteristic.

The main principles of OOP include:

• Encapsulation — combining data and methods into a single object.
• Inheritance — the ability to create new classes based on existing ones.
• Polymorphism — the ability of objects of different classes to respond to the same messages in different ways.

Classes serve as templates for creating objects and allow the implementation of these principles. However, in some languages (for example, Python), objects can be used without explicit class definitions (through functions, dictionaries, etc.), but this is no longer considered full-fledged OOP.

Thus, classes are a means of implementing OOP, but the concept itself is broader and includes object behavior and interaction between objects.