What are printers? A printer is an output device that prints characters, symbols, and perhaps graphics on paper. Printed output is generally called hard copy because it is relatively permanent in form. Softcopy refers to temporary images such as those displayed on a monitor. Printers are classified according to whether or not the image produced is formed by physical contact of the printing mechanism with the paper. Impact printers have contact; non-impact printers do not.
impact printers
An impact printer has mechanisms similar to those of a typewriter. It forms characters or images by striking a mechanism such as a hammer or printing wheel against an ink ribbon, leaving an image on the paper. Impact printers are disappearing; however, you can still contact a dot matrix printer. A dot matrix printer contains a print head of tiny pins that strike an ink ribbon, forming characters or images. Printheads are available with 9, 18, or 24 pins; the 24-pin head offers the best print quality. Dot matrix printers allow you to choose between draft quality output; A rougher-looking 72 dots per inch vertically, which may be acceptable for draft documents and reports, and a sharper-looking 144 dots per inch vertically, with near-letter quality, which is more suitable for showing a finished product to other people.
Dot-matrix printers print between 40 and 300 characters per second (cps) and can print some graphics, although reproduction quality is poor. Color ribbons are available for limited color use. Dot-matrix printers are noisy, inexpensive, and can print multi-part forms, creating multiple copies of a page at the same time, which low-impact printers can’t do.
Another type of impact printer is not used with microcomputers. Large computing facilities use high-speed line printers, which print a full line of characters at a time instead of a single character at a time. Some, called string printers, contain characters in a rotating string; others, called band printers, contain characters on a rotating band. These machines can reach speeds of up to 3,000 lines per minute.
Impactless Printers
Non-impact printers, now used almost everywhere, 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 that are commonly 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, like a copier, these images are created on a drum, treated with a magnetically charged ink-like toner (powder), and then transferred from the drum to paper.
– There are good reasons why laser printers are so popular. They produce crisp, sharp images of both text and graphics, providing resolutions from 300 dpi to 1200 dpi, which is near typographic quality (NTQ). They are quiet and fast. They can print 4 to 32 text-only pages per minute for individual microcomputers and more than 120 pages per minute for mainframes. (Pages with more graphics print more slowly.) They can be printed in many fonts (font styles and sizes). The more expensive models can print in different colors.
– Laser printers have built-in RAM chips to store the documents that come out of the computer. If you’re desktop publishing and printing complicated documents with color and lots of graphics, you’ll need a printer with lots of RAM. Laser printers also have their own ROM chips to store fonts and their own little dedicated processor. In order to handle complex page layouts and graphics, a laser printer works with a page description language, a type of software that has become a standard for printing graphics on laser printers. A PDL (Page Description Language) is software that describes the shape and position of letters and graphics on the printer. PostScript, from Adobe Systems, is a common type of page description language; HPGL, Hewlett-Packard Graphic Language, is another.
Inkjet printer: Like laser and dot matrix printers, inkjet printers also form images with small dots. Inkjet printers spray tiny electrically charged droplets of ink from four nozzles through holes in an array at high speed onto paper.
– Inkjet printers can print in color and are quieter and much less expensive than a color laser printer. However, they are slower and print at a slightly lower resolution (300-720 dpi) than lasers. Some new and expensive inkjet printers print up to 1200 or 1400 dpi. High-resolution output requires the use of special coated paper, which costs more than plain paper. And, if you’re printing high-resolution color graphics on an inkjet printer, the final output of a single page can take 10 minutes or more.
– A variation of ink jet technology is the bubble jet printer, which uses miniature heating elements to force specially formed inks through print heads with 128 tiny nozzles. Multiple nozzles print fine images at high speeds. This technology is commonly used in portable printers.
Aspects to consider when buying a printer, is it easy to configure the printer? Easy to operate? Do I need colour? or will black work? Does the manufacturer offer a good warranty and good telephone technical support? Otherwise, it is advisable to have your own personal printer and to know the answer to these questions.