Impact printers, which mostly have been superseded by ink-jet and laser printers, use a mechanical hammering device to produce each character. A formed character printer forces metal or plastic characters against an inked ribbon to produce a sharp image on paper; the characters may be on a moving bar, a rapidly rotating chain, a rotatable ball, or wheel spokes. A dot matrix printer uses a matrix of tiny pegs that, when hit from behind against a ribbon, impart a set of dots to form a character on the paper; a wide variety of characters and graphics is created using different dot combinations. Although noisy, impact printers can produce multiple copies of business forms simultaneously using carbon or carbonless techniques.
Nonimpact printers use thermal and electrostatic, rather than mechanical, techniques. Ink-jet printers, including bubble-jet printers, squirt heated ink through a matrix of holes to form characters or images. Laser printers form an image of the output on a selenium-coated drum using laser light that is turned on and off by data from the computer and then transfer the output from the drum using photocopying techniques. Thermal-wax-transfer printers and dye-sublimation printers use heat to transfer color pigment from a ribbon to a special paper to produce photographic-quality color images. Nonimpact printers are quieter than impact printers and produce higher quality output, especially of graphics, but at a greater cost per page.
See also laser printer.
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