2-program logic

1. Functions can be expanded

The core idea ：
abstract
Scalable
Function function

Relevant supplementary knowledge （ It is a very basic content of software engineering ）：
Common software architectures
Software development principles

2. recursive

Recursion is applied in actual work ： A tree structure

3. GDB debugging

step vs next
difference
step Single step function

GDB guide
GDB guide 2