Many library data processing systems are unresponsive to the needs of librarians because of the necessity to batch-process transactions in a computer center. Such systems tend to be reportoriented rather than information-oriented with resultant problems in the timeliness of information. Time-shared computing permits multiple users to process jobs simultaneously through on-line interaction with the computer. Such systems offer to the librarian the advantages of immediate access to information, costs shared with other users, and direct man-machine interaction. This tutorial paper describes time-shared systems with applications in the library. Problems concerning the cost and present state-of-the-art of time-sharing are discussed.