1. Book entry: the administrator can enter the information of new books, including the title, author, publishing house, ISBN number, etc.

2. Book retrieval: Users can retrieve books in the library through keywords, authors, ISBN and other information.

3. Borrowing management: users can borrow books and obtain corresponding borrowing vouchers and borrowing periods.

4. Return books: users can return the borrowed books to the library, and the administrator will handle them accordingly.

5. Reservation management: users can reserve books, and users will be informed to borrow them when they have books.

6. Book renewal: users can apply for an extension of the loan period. If no other users have reserved books, the administrator can approve the renewal.

7. User management: Administrators can manage readers' information, including registration, password modification and permission setting.

8. Overdue management: the system will record the borrowing period of readers, and once it is overdue, it will produce relevant overdue records and fine calculation.

9. Report statistics: the system can provide statistical reports such as borrowing records, borrowing volume and borrowing rate for administrators to analyze and manage.

10. Data backup and recovery: the system will back up data regularly to prevent data loss and recover it when necessary.

The above are just some common functions of library management system, and the actual functions will be different for different systems or institutions.