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Printers are one of the main output devices. it gives hard copy output. The output we get through this device is called hardcopy or hard output. Printers are classified into two categories on speed.
1) Daisy-Wheel printer:
The daisy-wheel 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 type.
Daisy–wheel printers are noisy and slow and can print from 10 to 75 characters per second. This type of printer can not print graphics.
2) Dot-Matrix printer:
A Dot-matrix printer produces character by striking pins against an ink ribbon. Each pin makes a dot and a combination of dots form characters. the print head is a type of these printer that consists of a matrix of tiny needles, typically seven rows with nine needles in each(9*7 matrix).
Dot-matrix printers are inexpensive and relatively fast (can print 50 t0 500cps) and noisy also.
1) ink-jet printer:
The ink-jet printer is called a non-impact printer because they print by spraying ink on paper and, prints characters by spraying small drops of ink on a sheet of paper. The ink is different from normal ink having a high iron content. There are magnetized plates in the ink’s path that direct the ink onto the paper in the desired shapes. Ink-jet printers can also print in high color, which makes them popular for home users. Although ink-jet printers are inexpensive and produce excellent output, they are slow. But it can not be used to produce multiple copies of a document in a single printing.
2) Laser printer:
Laser printers work like photocopy machines. the laser printer uses a laser beam to produce the image. The laser printer can produce very high-quality print and are capable of printing an almost unlimited variety of fonts. The light of the laser alters the electrical charge on the drum wherever it hits. These charges attract toner, which is transferred to the paper and fused to the surface by a heat process. laser printers are faster and more expensive than others. The Laser print quality is measured in the number of dots per inch(dpi) i.e. The Best laser printer can produce 600dpi or more.
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