Many printers are primarily used as local computer peripherals, and are attached by a printer cable to a computer which serves as a document source. Some printers, commonly known as network printers, have built-in network interfaces (typically wireless or Ethernet), and can serve as a hardcopy device for any user on the network. Individual printers are often designed to support both local and network connected users at the same time. Many modern printers can directly interface to electronic media such as memory sticks or memory cards, or to image capture devices such as digital cameras, scanners; some printers are combined with a scanners and/or fax machines in a single unit.
There are several types of printers
- daisy-wheel Similar to a ball-head typewriter, this type of printer has a plastic
or metal wheel on which the shape of each character stands out in relief. A hammer presses the wheel against a ribbon, which in turn makes an ink stain in the shape of the character on the paper. Daisy-wheel printers produce letter-quality print but cannot print graphics.
- dot-matrix:: Creates characters by striking pins against an ink ribbon. Each pin
makes a dot, and combinations of dots form characters and illustrations
- ink-jet: Sprays ink at a sheet of paper. Ink-jet printers produce high-quality
text and graphics
- laser: Uses the same technology as copy machines. Laser printers produce
very high quality text and graphics
- LCD & LED: Similar to a laser printer, but uses liquid crystals or light-
emitting diodes rather than a laser to produce an image on the drum.
- line printer: Contains a chain of characters or pins that print an entire line at
one time. Line printers are very fast, but produce low-quality print.
- thermal printer: An inexpensive printer that works by pushing heated pins
against heat-sensitive paper. Thermal printers are widely used in calculators and fax machines.
Printers are also classified by the following characteristics:
- quality of type: The output produced by printers is said to be either letter
quality (as good as a typewriter), near letter quality, or draft quality. Only daisy-wheel, ink-jet, and laser printers produce letter-quality type. Some dot-matrix printers claim letter-quality print, but if you look closely, you can see the difference.
- speed: Measured in characters per second (cps) or pages per minute (ppm), the
speed of printers varies widely. Daisy-wheel printers tend to be the slowest, printing about 30 cps. Line printers are fastest (up to 3,000 lines per minute). Dot-matrix printers can print up to 500 cps, and laser printers range from about 4 to 20 text pages per minute.
- impact or non-impact: Impact printers include all printers that work by
striking an ink ribbon. Daisy-wheel, dot-matrix, and line printers are impact printers. Non-impact printers include laser printers and ink-jet printers. The important difference between impact and non-impact printers is that impact printers are much noisier.
- graphics: Some printers (daisy-wheel and line printers) can print only text.
Other printers can print both text and graphics.
- fonts : Some printers, notably dot-matrix printers, are limited to one or a few
fonts. In contrast, laser and ink-jet printers are capable of printing an almost unlimited variety of fonts. Daisy-wheel printers can also print different fonts, but you need to change the daisy wheel, making it difficult to mix fonts in the same document.
|
