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Fundamentals of Dot Matrix Printkg
Figure 6-3. The nine rows of the matrix correspond to the nine pins on the
print head. For this uppercase letter, only the top seven pins fire - all at once
for each vertical line in this letter, and a single pin (firing repeatedly as the
print head moves sideways) for the horizontal line.
This printing technology is called impact, dot matrix printing.
Dots are printed according to a predesigned matrix or grid system.
Each letter, numeral, punctuation mark, and other special
character is formed by the arrangement of 4 to 36 dots.
The firing patterns for each character are pre-programmed in
Gemini and stored in “firmware” (ROM’s). By sending the
appropriate control codes to Gemini, we manipulate both the
number of pins fired and the order in which they are fired. If you
know which control code to send from your computer’s keyboard,
through the computer to the printer, you can even create new
“characters” by controlling the firing pins.
THE PkNT MATRIX
Let’s turn to Appendix K and look briefly at the dot patterns of the
various characters. All these characters, during the “normal”
printing mode (standard and italic), are constructed within a !5dot-
wide by g-dot-high matrix of “boxes? All the dots are positioned
vertically within one of the “boxes” in each column in the matrix.
Horizontally, the dots can be placed within any or all of the
five boxes across the row or on the lines separating the boxes. If
you thinkof the five boxes in a row as the “white” keys on a piano
and the lines between them as four “black” keys, you can “play”
a dot in any of the nine dot positions across a row. Thus, even
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