<P> In computing, input / output or I / O (or, informally, io or IO) is the communication between an information processing system, such as a computer, and the outside world, possibly a human or another information processing system . Inputs are the signals or data received by the system and outputs are the signals or data sent from it . The term can also be used as part of an action; to "perform I / O" is to perform an input or output operation . </P> <P> I / O devices are the pieces of hardware used by a human (or other system) to communicate with a computer . For instance, a keyboard or computer mouse is an input device for a computer, while monitors and printers are output devices . Devices for communication between computers, such as modems and network cards, typically perform both input and output operations . </P> <P> The designation of a device as either input or output depends on perspective . Mouse and keyboards take physical movements that the human user outputs and convert them into input signals that a computer can understand; the output from these devices is the computer's input . Similarly, printers and monitors take signals that a computer outputs as input, and they convert these signals into a representation that human users can understand . From the human user's perspective, the process of reading or seeing these representations is receiving input; this type of interaction between computers and humans is studied in the field of human--computer interaction . </P> <P> In computer architecture, the combination of the CPU and main memory, to which the CPU can read or write directly using individual instructions, is considered the brain of a computer . Any transfer of information to or from the CPU / memory combo, for example by reading data from a disk drive, is considered I / O . The CPU and its supporting circuitry may provide memory - mapped I / O that is used in low - level computer programming, such as in the implementation of device drivers, or may provide access to I / O channels . An I / O algorithm is one designed to exploit locality and perform efficiently when exchanging data with a secondary storage device, such as a disk drive . </P>

Term for input that is outside the model