Q. Input - output Devices using Device Controller?
A device controller needs not to necessarily control a single device. It can typically control multiple I/O devices. It comes in form of an electronic circuit board which plugs directly in the system bus and there is a cable from controller to every device it controls. Cables coming out of controller are typically terminated at back panel of main computer box in form of connectors called as ports.
The Figure below explains how I/O devices are associated to a computer system through device controllers. Please note the subsequent points in figure:
Figure: Connecting I/O Devices using Device Controller