Explain the main principles underlying the SOLID pattern in object-oriented programming.

The SOLID principles are a set of five fundamental object-oriented design rules that help create flexible and maintainable systems:

1. S — Single Responsibility Principle Each class should have only one reason to change, meaning it should be responsible for a single task.

2. O — Open/Closed Principle Classes should be open for extension but closed for modification.

3. L — Liskov Substitution Principle Subclass objects should be interchangeable with superclass objects without affecting the correctness of the program.

4. I — Interface Segregation Principle Clients should not depend on interfaces they do not use. It's better to have several specific interfaces than a single universal one.

5. D — Dependency Inversion Principle High-level modules should not depend on low-level modules directly; both should depend on abstractions.

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