III. OUTPUT HARDWARE

Output hardware consists of internal and external devices that transfer information from the computer’s CPU to the computer user. Graphics adapters, which are either an add-on card (called a video card) or connected directly to the computer’s motherboard, transmit information generated by the computer to an external display. Displays commonly take one of two forms: a video screen with a cathode-ray tube (CRT) or a video screen with a liquid crystal display (LCD). A CRT-based screen, or monitor, looks similar to a television set. Information from the CPU is displayed using a beam of electrons that scans a phosphorescent surface that emits light and creates images. An LCD-based screen displays visual information on a flatter and smaller screen than a CRT-based video monitor. Laptop computers use LCD screens for their displays.

Printers take text and image from a computer and print them on paper. Dot-matrix printers use tiny wires to impact upon an inked ribbon to form characters. Laser printers employ beams of light to draw images on a drum that then picks up fine black particles called toner. The toner is fused to a page to produce an image. Inkjet printers fire droplets of ink onto a page to form characters and pictures.

Computers can also output audio via a specialized chip on the motherboard or an add-on card called a sound card. Users can attach speakers or headphones to an output port to hear the audio produced by the computer. Many modern sound cards allow users to create music and record digital audio, as well.