An acronym for Basic Input/Output System. Mostly germane to PC compatible computers, this is usually an EPROM with computer program instructions in it. A computer motherboard BIOS controls how the hardware is defined and the basic functions of the computer (such as controlling the keyboard, monitor, etc.). With a SCSI host adapter, its BIOS is used to control SCSI hard disk drives and perform the boot function. If a host adapter does not have a BIOS, then hard disk drives controlled by that host adapter cannot be used to boot from (booting must be done from another source, such as floppy, IDE, or another SCSI host adapter with a BIOS). Hard drives can have their own BIOS as well, which defines their operation. The BIOS can also contain useful software utilities, and in some cases, can be reprogrammed or updated via software to accommodate new hardware. Older PC computers often have to have their BIOS updated in order to properly work with new hardware.