Output Devices, Continued
Printers provide a hard copy printout of data stored electronically inside the
computer or from a disk. The two types of printers are impact printers and
Impact printers operate in the same manner as do typewriters. They are
either front striking where a print hammer strikes a character against an inked
ribbon and paper or hammer striking where print hammers strike a character
against paper first and then an inked ribbon. Impact printers print one
character at a time at speeds from 30 to 350 characters per second (CPS).
Impact printers use standard single, multipart, and continuous-form paper.
Dot matrix printers and daisy wheel printers are impact printers.
A dot matrix printer creates a character with a series of tiny pins or wires
that strike the ribbon or page and leave an image in dots. The resolution of
the matrix is defined in terms of rows and columns of dots. A 7 by 9 matrix
uses seven dots horizontally and nine dots vertically to create a character.
Some dot matrix printers have a 36 by 24 matrix. The size of the matrix
determines the quality of the printed character. Dot matrix printers are near
letter quality, faster than daisy wheel printers, and have speeds ranging from
60 to 350 cps.
Figure 3-9 shows the letter L created by a dot matrix printer,
Figure 3-9. The letter L on a dot
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