PRINTERS

7/11/98

Printers: A number of technologies are used for printing on PCs. There are three primary approaches to printing. Character printers print a single character at a time. Line printers print a line at a time. Page printers print an entire page.

Character printers evolved from modified electric typewriters or teletype machines and are now dominated by matrix printers that fire 7 or more tiny hammers to print dots. 9 wire printers can print acceptable text and 24 wire printers can print usable graphics and excellent text. Character printers are generally inexpensive and are most useful for low to moderate quality text at low to moderate speed. They will print multipart forms.

Line printers typically use drums or chains with 128 or 132 individual sets of characters to print entire lines in a single pass. They are generally expensive, very fast and text only. they are used for high volume output in office applications. Multipart output can be generated.

Page printers print entire pages in one pass using laser, LED, or ink jet technology. They can produce excellent graphics output and very high quality text. High thruput laser printers are available, but expensive. Low cost units may have excellent quality, but low throughput and high cost per page. For the most part, page printers do not use impact technologies and therefore can not do multipart output.

All types of printers come in both serial and parallel versions with parallel versions usually being somewhat faster. Graphics mode printout -- including much page printing -- tends to be slow because of the need to pass large amounts of data to the printer. A few printers require IEEE-1284 ports and cabling that allow two way communication and fast output through a PC parallel port. Presumably, printers supporting USB connections will soon be available.

Character and Line printer throughputs generally are specified in characters per second. General purpose character printers usually can print 50 to several hundred characters per second depending on quality. Older or special function printers may be slower. Some printers when used for high volume output, may eventually detect head overheating and will slow to a reduced output rate periodically while the print head cools.

Page printers are rated in pages per minute and print at rates varying from one or two PPM for workstation units to 20 or more ppm for high end workgroup units. There is no standardized "page". For marketing reasons, vendors typically define a page optimistically -- a single page of text using an installed or preloaded font without graphics. 1PPM is probably roughly equivalent to 50-100cps for a character printer.

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