In computing, an input device is any peripheral (piece of computer hardware equipment) used to provide data and control signals to an information processing system such as a computer or other...
An input device is any device that is used to provide data and control signals to an information processing system. Examples:
Keyboard Mouse Microphone Web cam
An output device is any computer...
I'm not sure what you mean. As far as I am aware, there exists an input for every output, and vise versa. Speakers <-> MicrophoneMonitor <-> ScannerPrinter <-> DigitizerText...