This standard defines an input/output bus for interconnecting computers and peripheral devices. It defines extensions to the Small Computer System Interface (ISO 9316:1989), referred to herein as SCSI-1. It also provides more complete standardization of the previously defined command sets. It includes the necessary specification of the mechanical, electrical, and functional characteristics of the interface to allow inter-operability of conforming devices. This standard is referred to herein as SCSI-2. The term SCSI is used wherever it is not necessary to distinguish between the two versions.