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A printer is an output device that produces a hard copy of data. The resolution of printer output is expressed as DPI. Printers can be classified into different types in several ways. First, the printers can be divided into three categories by the way they print.
Second, printers can be classified into two forms according to the use of a hammer.
Another classification can be made by the way they form characters.
Microcomputers use five kinds of printers. They are daisy wheel printers, chain printers, dot-matrix printers, ink-jet printers, and laser printers.
Daisy-Wheel Printer
Daisy-Wheel is a printer mechanism that uses any kind of hub (wheel) having a set of spokes at the margin of the hub. The wheel can be removed to use a different character set. The end of each spoke is a raised image of a type character. When the wheel is turned and the required character is aligned to the print hammer, the character is then struck into a ribbon and onto a paper with the hammer.
Daisy-Wheel Printer prints typewriter-like very high quality characters. However, they are slower and less reliable than dot-matrix printers. Microcomputer users seldom use this printer, because the better dot-matrix printers and inexpensive laser printers are available today.
Chain Printer
A chain printer uses a printing mechanism that uses character typefaces linked together in a chain. The chain spins horizontally around a set of hammers aligned with each position. When the required character is in front of the selected print position, hammer in that position hits the paper into the ribbon against the character in the chain.
This printer is not commonly found around microcomputers, because it is a very expensive, high-speed machine designed originally for mainframes and minicomputers. Chain printers are very reliable and can speed up to 3000 lines per minute.
Dot-Matrix Printer
Dot-matrix printers are printers that write characters and form graphic images using one or two columns of tiny dots on a print head. The dot hammer moving serially across the paper strikes an inked-ribbon and creates images on paper.
Dot matrix printers are popular printers used with microcomputers, because the printers are highly reliable and inexpensive. They are used for tasks where a high-quality image is not essential. Many users, however, move from dot printers to laser printers, because the price of laser printers is falling down. Several kinds of dot matrix printers are available with print heads that have 7, 9, 18, or 24 pins.
Ink-Jet Printer
Ink-jet is a printer mechanism that sprays one or more color of ink at high speed onto the paper and produces high-quality printing. This printer also produces color printing as well as high-quality image. That is, ink-jet printers can be used for variety of color printing at a relatively low cost. Ink-jet printing has two methods: Continuous stream method and drop-on- demand method.
Laser Printer
A laser printer is a printer that uses the electrophotograpic method used in a copy machine. The printer uses a laser beam light source to create images on a photographic drum. Then the images on the drum are treated with a magnetically charged toner and then are transferred onto a paper. A heat source is usually applied to make the images adhere.
In 1984, Hewlett-Packard introduced the first desktop laser printer, called the LaserJet. The laser printer revolutionized personal computer printing and has spawned desktop publishing.
The laser printer produces high-resolution letters and graphics quality images, so it is adopted in applications requiring high-quality output. Although a high-priced color laser printer is also available in the market, a less expensive, desktop gray scale laser printer is widely used. Recently, the laser printer is gaining its market share dramatically, mainly because the lowered price and the quality.