What's an I/O Device? When it comes to the computing world, a keyboard or a mouse could be an input device for a computer, where those input signals are processed, and monitors and printers are the output devices. However, machine builders and discrete manufacturers have many more complex and sophisticated control signals to deal with. There also are many more options regarding the type of I/O technology and devices to choose from depending on the users' needs. Tell us what is an I/O device and how it helps you do your job better.