(Abbreviation for Input Output) Input Output deals with 2 out of 3 of the activities (input, processing, and output) performed by a PC . I/O are complimentary tasks of gathering data for the microprocessor to work with and making the results available to the user through a device such as the monitor or printer. The keyboard and the mouse are input devices that make information available to the computer; the display and printer are output devices with which the computer makes its results available to the user. The Hard Disk is both an input and an output device because it can either provide stored information or store the data after processing.