Problem: Using singly linked list, create a C program that simulates an inventory system. The program must meet the following requirements:

1. Ability to add an Item

2. A feature to search a particular item based on its property (atleast three) and display its properties. (i.e., number of stocks, item code, description)

3. Add/subtract stocks of an item

4. View all items

5. Remove an item

6. Modify an item

7. Register and Login feature (use a separate structure for users)

8. Main Menu once user has been verified.

Program Flow:

1. The first menu will provide two options: login and register
2. Once registered, user can use his/her credential to use the system
3. For verified user, display the main menu for inventory
4. Display a warning/error for unverified user
5. No item can be added in the structure if the item code already exists
6. No user can be registered if the username already exists