The two types of printers are impact and non-impact printers. Impact Printers can produce a page, a line, or a character at a time while Non-impact printers can produce both text and graphics.
It is considered to impact printers when part of the printer presses the paper to form the character. Impact printers can produce carbon copies and are noisy, although covers are available to muffle the noise. In contrast, the nonimpact printer can’t produce carbon copies. This is usually not a problem because it’s easy to produce multiple originals, but sometimes carbons are required for legal purposes.
Impact Printers can produce a page, a line, or a character at a time. Large computers use line printers that can crank out a hard copy at a rate of 3,000 lines per minute. Print quality is low, but these printers are mainly used for printing backup copies of large amounts of data. Still used in some law offices are letter-quality printers, which closely resemble office typewriters (except that they are controlled by the computer).
In decreasing use are dot-matrix printers, which were once the most popular type of printer used with PCs. If you use a magnifying glass to look at a report created with a dot-matrix printer, you can see the small dots forming each character. The least expensive dot-matrix printers print using a matrix of 9 pins and produce poor quality printouts. Better dot-matrix printers use a 24 pin print head and can produce near-letter-quality printouts (printouts that look almost as good as printed text). Quality may still be poor, however, if the ribbon needs replacing, which is often the case for dot-matrix printers located in college computer labs. Some professors will not accept papers printed on any kind of dot-matrix printer because the output is so difficult to read.
Non-impact printers are the most widely used printers for PCs today. Non-impact printers can produce both text and graphics. Because nothing strikes the paper, non-impact printers are quiet. Some of the most popular non-impact printers are laser printers and inkjet printers.
Inkjet printers (also called bubble-jet printers) are the least expensive (and most popular) non-impact printers. Like dot-matrix printers, inkjet printers work by forming an image that is composed of tiny dots, but the dots are much smaller and more numerous. The result is a printout that’s difficult to distinguish from the fully formed characters printed by laser printers. Inkjet printers can also print in color, which makes them popular choices for home users. Earlier inkjets had problems with smudging, but new ink formulations have all but eliminated this problem. Although inkjet printers are inexpensive and produce excellent output, they are slow, and per-page costs may exceed the costs of running a laser printer due to the generally high cost of ink cartridges.
Laser printers work like copy machines. Under the printer’s computerized control, a laser beam creates electrical charges on a rotating print drum. These charges attract toner, which is transferred to the paper and fused to its surface by a heat process. In contrast to inkjets, laser printers print faster; some can crank out 18 or more pages per minute. Although they are more expensive initially than inkjet printers, laser printers generally have lower per-page costs.
Laser printers come in a variety of sizes; generally, the larger and faster the printer, the more expensive it is. Large laser printers are used on mainframes and minicomputers where high-quality graphic output is required. Incorporate networks, high-volume network laser printers take care of the printing needs of entire departments. Smaller, personal laser printers are available for individual use. Color laser printers are available, but they are expensive. Laser printer quality is judged by the number of dots per inch (dpi) that the printer can produce. The least expensive laser printers can generate 300 dpi, which is adequate for text (but not for graphics). The best laser printers can produce 600 dpi or more.
The best color printers are thermal transfer printers. These printers use a heat process to transfer colored dyes or inks to the paper’s surface. Because the colors run together, thermal transfer printers do a much better job of printing photographs and artwork than other computer printers. The best results, however, require glossy paper, which is expensive. The best thermal transfer printers are called dye-sublimation printers. These printers are slow and expensive, but they produce results that are difficult to distinguish from high-quality color photographs. Less expensive are snapshot printers, which are thermal transfer printers designed to print the output of digital cameras at a maximum size of 4 by 6 inches.
Multifunction printers combine inkjet or laser printers with a scanner, a fax machine, and a copier, enabling home office users to obtain all these devices without spending a great deal of money.
A plotter, like a printer, produces an image by physically moving a pen over a sheet of paper. A continuous-curve plotter is used to draw maps from stored data. Computer-generated maps can be retrieved and plotted or used to show changes over time. Plotters are generally more expensive than printers.