Device controller

A device controller is a peripheral which is an intermediary between a computer (usually connecting to a bus, although possibly the CPU directly) and some external device (often secondary storage).

The canonical pairing is a disk controller and a disk drive, although controllers are also found with magnetic tape drives, paper tape readers and/or punches, and numerous other kinds of devices.

Usually a single controller is able to handle multiple identical devices, thereby amortizing the controller's cost, since the external devices often include mechanical components, and are the thus slower than the all-electronic controller.