To be useful, a computer must have some means of acquiring new data to operate on and of producing results for eventual human consumption. These functions are called input and output, collectively Input/Output or just I/O. Many devices facilitate these functions, including I/O Devices such as keyboards and printers, Interfaces that connect these devices to the central processing unit, and I/O Controllers that manage the flow of data among them.
This is a very cleverly named page. (If you didn't know that it was cleverly named, please see naming conventions. Or just click on the "Input" link at the top of this page. :-) )