What are the SOLID principles of object-oriented design?

The SOLID principles are a set of five design principles for creating maintainable and flexible software:

1. Single Responsibility Principle (SRP): A class should have only one reason to change, meaning it should have a single responsibility.
2. Open/Closed Principle (OCP): Software entities (classes, modules, functions) should be open for extension but closed for modification.
3. Liskov Substitution Principle (LSP): Subtypes must be substitutable for their base types without affecting the correctness of the program.
4. Interface Segregation Principle (ISP): Clients should not be forced to depend on interfaces they do not use. Keep interfaces focused and specific.
5. Dependency Inversion Principle (DIP): High-level modules should not depend on low-level modules. Both should depend on abstractions. Abstractions should not depend on details; details should depend on abstractions.

These principles help guide the design of object-oriented systems to be more modular, maintainable, and adaptable.