接口如何降低模块之间以及与外部环境之间连接的复杂性？

Question

As I read in CHAPTER 13 DESIGN CONCEPTS AND PRINCIPLES

Book: Software Engineering A PRACTITIONER'S APPROACH by Roger S. Pressman,FIFTH EDITION:

6.A design should lead to interfaces that reduce the complexity of connections between modules and with the external environment

How interfaces reduce the complexity of connections between modules and with the external environment?

Answer 1

I guess that instead of describing all possible connections thanks to specific types, you simply have to describe them with interfaces and then at the implementation step all you need is to be sure that your type implementing the dedicated interface.

Here two examples: 1) Without using interfaces

2) using interfaces

Hoping it is clear,

Regards,

EBR