Input and output devices are computer hardware components. An input device is a component used to feed information to a computer, whereas an output device gives processed information back to the user.
The most common input devices are the keyboard, mouse, scanner, webcam, microphone and joystick. Output devices typically include the display monitor, speaker and printer.
In computing, input devices are used before output devices. A user uses the keyboard and mouse to type in and navigate to a video on the Internet. The processor processes the information and plays the video back as moving images on screen and accompanying audio on the speakers.
Input devices are physically interacted with by the user and have buttons, keys, a lens or some other component that is responsible for the actual data input. Output devices are never contacted, are usually larger, and typically have a screen or set of speakers for data output.
Data output can be of two different types. When a monitor shows an open document, it is known as a "soft copy" because the image can be replaced by closing the window. When a printer prints the document, it is known as a "hard copy" because the printed information is permanent and cannot be replaced.
Input devices are usually cheaper than output devices.