A printer is an output device that prints characters, symbols, and perhaps graphics paper. Printers are categorized according to whether or not the image produced is formed by physical contact of the print mechanism with the paper. Impact printers have contact; non impact printers do not.
Impact Printer: An impact printer has mechanisms resembling those of a typewriter. It forms characters or images by striking a mechanism such as a print hammer or wheel against an inked ribbon, leaving an image on paper. Following are the impact printers:
- Dot-matrix printer: A dot-matrix printer contains a print head of small pins that strike an inked ribbon, forming characters or images. Print heads are available with 9, 18, or 24 pins; the 24-pin head offers the best print quality.
- High-speed line printers: Another type of impact printer is not used with microcomputers. Large computer installations use high-speed line printers, which print a whole line of characters at once rather a single character at a time.
Non impact printers: Non impact printers, used almost everywhere now, are faster and quieter than impact printers because they have fewer moving parts. Non impact printers form characters and images without direct physical contact between the printing mechanism and the paper. Two types of non impact printers often used with microcomputers are laser printers and ink-jet printers:
- Laser Printer: Like a dot-matrix printer, a laser printer creates images with dots. However, as in a photocopying machine, these images are created on a drum, treated with a magnetically charged ink-like toner (powder), and then transferred from drum to paper.
- Ink-Jet printer: Like laser and dot-matrix printers, ink-jet printers also form images with little dots. Ink-jet printers spray small, electrically charged droplets of ink from four nozzles through holes in a matrix at high speed onto paper.