Your PC sends a series of series of hexadecimal ASCII codes that
represent characters, punctuation marks, and printer movements such
as tabs, carriage returns, line feeds and form feeds that control
the position of the print head in relation to the paper.
2]The ASC II coded are stored in a buffer, which is a special section
of the printer's random access memory (RAM). Because it usually
takes longer for a dot-natrix printer to print character than it
takes a PC and software to send those character to the printer,
the buffer hepls free up the PC to perform other functions during
the buffer gets full, the printer sends an XOFF control code to
the computer to tell it to suspend its stream of data. When the
buffer fress up space by sending some of the chracters to its processor,
the printer sends an XON code to the PC, which resumes sending data.
3]Among other codes are commands that tell printer to use a certain
fonts's bitmap table, which is contained in the printer's read-only
memory chips. That table tells the printer the pattern of dots that
it should use to create the character represented by the ASC II
4] The printer's processor takes the information provided by the
bitmap table for an entire line of type and calculates the most
efficient path for the print head to travel. Some lines may be printed
from roght to left. The processor sends the signals that fire the
pins in the print head, and it also controls the movement of the
print head and platen.
5] Electrical signals from the processor are amplified and travel
to certain of the circuits that lead to the print head. The print
head contains 9 or 24 wires, called printing-pins, that are aligned
in one or two straight lines. One end of each of the pins is matched
to an individual solenoid, which creates a magnetic field that repels
a magnet on the end of the pin, causing the pin to race toward the
6] The moving pin strikes a ribbon that is coated with ink. The
force of the impact transfers ink to the paper on the other side
of the ribbon. After the pin fires, a spring pulls it back to its
original position. The print head continues firing different combination
of print wires as it moves across the page so that all characters
are made up of various vertical dot patterns. Some printers improve
print quality or create boldface by moving the print head through
a second pass over the same line of type to print a secong set of
dots that are offset slightly from the first set.
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