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:

• Every I/O device is linked through a hardware interface known as I/O Port.
• Single and Multi-port device manages single or multi-devices.
• Communication between Memory and I/O controller is through bus only in case of Direct Memory Access (DMA) whereas path passes through CPU for these kind of communications in case of non-DMA.

Figure: Connecting I/O Devices using Device Controller