(Or "hard disk controller", HDC) The circuit which allows the CPU to COMmunicate with a {hard disk}, {floppy disk} or other kind of {disk drive}. The most COMmon disk controllers in use are IDE and SCSI controllers. Most home personal COMputers use IDE controllers. High end PCs, workstations and network {file servers} mostly have {SCSI adaptors}. (1998-03-16)