Explain what each of the SOLID principles used in object-oriented system development means.

SOLID principles are a set of guidelines for designing flexible and maintainable object-oriented systems:

• S (Single Responsibility Principle) — the principle of single responsibility. Each class should have only one reason to change, meaning it should be responsible for a single specific task.

• O (Open/Closed Principle) — the principle of openness/closure. Classes should be open for extension but closed for modification, allowing functionality to be added without changing existing code.

• L (Liskov Substitution Principle) — the principle of Liskov substitution. Subclass objects should be interchangeable with objects of the superclass without affecting the correctness of the program.

• I (Interface Segregation Principle) — the principle of interface segregation. Clients should not depend on interfaces they do not use; it is better to have several specialized interfaces than one general interface.

• D (Dependency Inversion Principle) — the principle of dependency inversion. 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.