The need for input and output devices
Introduction
Computer systems are digital devices. They use electrical signals to indicate patterns of ones and zeros and it is these patterns which it works on. Humans are not digital! Humans use words, sounds, videos and images, for example, to give meaning to ideas. So how can a human, which doesn't use and understand digital signals get data into a computer, which doesn't understand words, sound, videos and pictures? And once data has entered a computer and has been processed in some way, how can a computer then change its digital signals into a form that gives meaning to humans? The answer is to use input and output devices.
Input devices
Input devices take data in whatever form from the outside world and convert it into a digital format, which can then be used and processed by a computer. Common input devices include mice, keyboards, microphones and sensors.
Output devices
Once processed, output devices take a computer's digital signals and convert them into a form that can be interpreted by a human. Common output devices include Visual Display Units (otherwise known as VDUs, monitors or screens), printers and headphones.