Table of Contents
Advertisement
Chapter 4
Each pin is driven by a "gun," or electromagnet, which "fires" when told to do
so by the electronics inside the printer. The printer electronics responds to
those ASCII code instructions we send from the computer in the form of
"ASCII numbers."
For example, to print the letter "I." wires 1 and 7 are fired first. They hit the
ribbon, which makes marks on the paper where the left top and bottom of the
letter "I" should be.
The head then shifts over a bit and wires 1,2,3,4,5,6 and 7 all fire at once,
printing the center of the letter "I." One more shift and one more shot of
needles 1 and 7 and the letter "I" is complete. (Figure 4-2).
This is called "dot matrix" printing. Dots are printed according to a pre-
designed "matrix" or "grid" system, where each letter, number, and punctua-
tion mark is formed by an arrangement of dots. As we have seen, this complex
printing process takes place
The pins fire only in groups or clusters. The firing patterns are already pro-
grammed inside the printer, matching the alphanumerics (letters and numbers)
and symbols found in our ASCII charts. No, we cannot fire an individual
needle yet, but that's what all this is leading up to.
Appendix C shows all our alphanumeric characters constructed within a 7 dot
high by 5 dot wide matrix. Every letter, number, and punctuation character is
designed to fit within that box.
Notice that the sixth column is always empty. In fact, it isn't even shown. It's
reserved for horizontal spacing between characters.
Our smallest alphanumeric character, the period, requires only 4 dots in a 2 by 2
grid. Our highest "resolution" in the non-graphic mode is therefore 4 dots.
32
Figure 4-2
quickly.
very
Advertisement
Table of Contents
