The input devices, such as mouse and keyboard, can send data to a computer system but cannot receive from. On the contrary, the output devices such as monitors and printers receive data from a computer, usually for the purposes of displaying. In this perspective, webcam, barcode reader, microphone, scanners, and sensors (e.g. heat  or humidity) are the examples of input devices. Headphone, projector, speaker, printer, monitor are the examples of output devices.