What are the main principles of OOP? Explain the SOLID principles in your own words.

The main principles of OOP are:

• Encapsulation — hiding the internal implementation of an object and providing access only through methods.
• Inheritance — the ability to create new classes based on existing ones, inheriting their properties and methods.
• Polymorphism — the ability of objects of different classes to respond to the same messages (methods) in different ways.
• Abstraction — highlighting common characteristics and behaviors, hiding implementation details.

The SOLID principles are a set of guidelines for writing flexible and maintainable code:

• S (Single Responsibility Principle) — a class should have only one responsibility.
• O (Open/Closed Principle) — software entities should be open for extension but closed for modification.
• L (Liskov Substitution Principle) — objects of subclasses should be interchangeable with objects of the base class without breaking the logic.
• I (Interface Segregation Principle) — it is better to have many specialized interfaces than a single universal one.
• D (Dependency Inversion Principle) — upper-level modules should not depend on lower-level modules; both should depend on abstractions.

These principles help create code that is easier to test, extend, and maintain.