Also known as: I/O, input/output, input output
Input/output (I/O) is the set of channels through which a computer takes in and sends out data — everything that connects the CPU to the world beyond the chip.1
Overview
Input brings data in: a keyboard, a mouse, a microphone, a sensor reading, a packet arriving on the network. Output sends data back out: pixels to a screen, sound to a speaker, a packet onto the network, a signal to an actuator. Many channels are bidirectional — USB and network ports carry data both ways.
A computer with no I/O is sealed off and useless; I/O is what lets it observe and act.
Where it fits
I/O is one of the four building blocks of computer hardware. On a desktop the channels are mostly USB, video, and network. On small devices like a single-board computer or a microcontroller, the most direct form of I/O is GPIO — general-purpose pins wired straight to sensors and actuators.
Sources
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Input/output — Wikipedia, on the channels a computer uses to communicate with the outside world. ↩