Learn the definitions and examples of input , output and input / output devices . Input devices send data to a computer, output devices display or reproduce data, and input / output devices do both. Input and output devices are essential components of a computer system, each serving distinct functions in the process of data handling and communication. Input devices allow users to provide data and instructions to a computer, while output devices present processed data in a user-friendly form. The functioning of a computer system is based on the combined usage of both input and output devices . Using an input device we can give instructions to the computer to perform an action and the device reverts to our action through an output device .