Explain the differences between Dependency Inversion and Dependency Injection principles and how they relate to modular system design.

Dependency Inversion Principle (DIP) is one of the SOLID principles, which states that:

• 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.

This helps reduce coupling and increase system flexibility.

Dependency Injection (DI) is a specific pattern or technique implementing DIP. DI means that dependencies (objects needed by a class) are passed to it from outside, rather than created inside the class.

For example, instead of the class creating a dependency object itself, it receives it through a constructor, setter, or method.

In the context of designing modular systems, DIP sets an architectural principle, and DI is a way to implement it, which facilitates testing, reuse, and maintenance of code.