A peripheral device (this can be a barcode reader, a graphics tablet, a keyboard, a magnetic stripe reader, a modem, a mouse, a scanner, or a stylus) enters data or instructions into a computer for viewing, processing, storage, output, or transmission.
Input devices convert user actions and analog data (sound, graphics, images) into digital electronic signals that can be processed by a computer. Digital data (e.g. from barcode readers, modems, scanners, etc.) does not require conversion and is entered directly into a computer. It is through input devices that a user exercises control over a computer, its operations and outputs.