Abstract: An on-line computerized system useful in automatic document control and inventory systems such as that needed in libraries with a large number of books, records, films, and other items. In the library system disclosed, each borrower and each item within the library is given a unique identification number. The system includes automated Check-In/Check-Out terminals at each branch library which are interfaced to a computer for facilitating patron services and permitting fast, on-line storage and retrieval of data concerning overdue fines, reserve books, expired and delinquent patron cards, and other pertinent information.