PC Hardware A Beginner’s Guide

(^404) PC Hardware: A Beginner’s Guide
Dot Matrix Printers
The next printer to emerge was the dot matrix printer, which, as discussed in more detail
later in the chapter, creates a pattern of dots that are arranged to produce alphabetic, nu-
meric, and graphical characters on the printed document. While still somewhat noisy, the
dot matrix printer was much faster and much quieter than the daisy wheel. In addition,
the dot matrix printer incorporated a mechanism that feeds continuous-form paper while
keeping it properly aligned.
The Centronics Corporation developed the first popular dot matrix printers for the
early Apple computers. These printers were very simple to operate through a front panel
menu pad that included only choices for online/offline, line feed (to advance the paper a
single line), and form feed (to advance the paper one page). When the printer was online,
it received printing instructions from the computer indicating whether the characters to
be printed were letters, numbers, or punctuation. The connector used on the printer’s end
of the cable that attached the printer to the computer was a distinctive 36-pin connector
that featured pins arranged on a center bar (see Figure 17-2).
The dot matrix printer has been largely replaced by inkjet and laser printers in the
home and small office. However, because it is an impact printer (it prints with a mechani-
cal device that physically strikes the paper) and because it can accurately feed multipart
continuous forms, the dot matrix printer continues to have a market. Many printer manu-
facturers,includingIBM,Epson,andLexmark,stillofferfulllinesofdotmatrixprinters.
Figure 17-2. A printer cable with a 36-pin Centronics head on one end and a DB-25
connector on the other