C Login System with Hash Tables

I need help completing 7 functions in the provided hash_table.c file to create a C-based login system using hash tables. The functionalities include user registration, password checking, and file loading.

Key Requirements:
- User registration
- Password checking
- File loading/saving of user data

Ideal Skills:
- Proficiency in C programming
- Experience with hash tables
- Familiarity with file I/O in C

Please provide a brief overview of your experience and approach.