The library's database would have files (tables) containing details about the:
Information Retrieval: Librarians need to be able to find out whether books are currently in stock or out on loan - searches have to be performed on the database.
There may also be a link to other libraries so that if a title is available there, it can be requested and transferred between libraries.
Process: The computer system will need to be able to calculate which books are overdue and whether any fines are due. Output: Summary reports, results of searches.
Library systems work in real-time as data is updated immediately books are loaned.