This standard defines the AT Attachment Interface. This standard defines an integrated bus interface between disk drives and host processors. It provides a common point of attachment for systems manufacturers, system integrators, and suppliers of intelligent peripherals. This standard was developed by Task Group X3T9.2 of Accredited Standards Committee X3 during 1986-90. The standards approval process started in 1991. This document includes annexes which are informative and are not considered par of the standard. Requests for interpretation, suggestions for improvement and addenda, or defect reports are welcome. They should be sent to the X3 Secretariat, Computer and Business Equipment Manufacturers Association, 1250 Eye Street, NW, Suite 200, Washington, DC 20005-3922. This standard was processed and approved for submittal to ANSI by Accredited Standards Committee on Information Processing Systems, X3. Committee approval of the standard does not necessarily imply that all committee members voted for approval. At the time it approved this standard, the X3 Committee had the following members: