[Technical Summary] C++-based on polymorphic staff management system

Sum up and learn a project of c++ at station b: https://www.bilibili.com/video/BV1t5411n7kX?p=81

Summarize the knowledge points here.

1. This project mainly uses polymorphism: pointers to parent classes or references to objects in subclasses;

2. Memory management;

3. Use a management class to manage some operations; use specific methods in this class to complete the corresponding functions;

4. Document management;

5. Standardized writing;