1. Input devices allow users to enter data and instructions into a computer and include keyboards, mice, touchscreens, barcode readers, digital cameras, trackballs, scanners, microphones, and video cameras. 2. Output devices convey processed information from the computer to users and include computer monitors, printers, plotters, speakers, headphones, and microfilm devices. 3. Common input devices allow entering of text, numbers, images, audio, and video as well as programs and commands. Common output devices visually display information on screens or print it on paper.