Printing Machine

A device that prints text or illustrations on paper. There are many different types of printers. In terms of the technology utilized, printers fall into the following categories:

1.) 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.

2.) dot-matrix: Creates characters by striking pins against an ink ribbon. Each pin makes a dot, and combinations of dots form characters and illustrations.

3.) ink-jet: Sprays ink at a sheet of paper. Ink-jet printers produce high-quality text and graphics.

4.) laser: Uses the same technology as copy machines. Laser printers produce very high quality text and graphics.

5.) 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.

6.) 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.

7.) 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:

1. 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.

2. 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.

3. 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.

4. graphics: Some printers (daisy-wheel and line printers) can print only text. Other printers can print both text and graphics.

5. 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.