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Figure 9-5. Later in this chapter we’ll use this character to create
a small graph.)
You’ll notice that Figure 9-4 includes a lot of information
around the grid. Don’t be intimidated; we’ll explain each item
as we come to it in our discussion of defining and actually printing
download characters. You may have noticed another difference
between this grid and the one shown in Figure 9-3: it’s only eight
boxes high. Which leads us to...
m, m, m, m, n m, m, m. m, m,, m,,
32
16
6
4
2
1
Total
ASCII Code
Descender
Star1 column
End column
M, = Descender + 126 + (Start * 16) + End
Figure 9-4. Use this grid (or one similar to it) to define your own
characters.
n Rule 1: Download characters are eight dots high
As you noticed in Figure 9-2, capital letters, most lowercase
letters, and most special characters.use only the top seven pins
of the printhead. Download characters can go one better: they
can use as many as eight of the nine wires in the print head. So
our grid is eight dots high.
It’s also possible to use the bottom eight pins, just as the “g”,
““3 ‘6 3.
J- P*
“q”, and “y” of the standard character sets do. These
are called descenders (because the bottom of the character de-
scends below the baseline of the rest of the characters).
One bit in the download character definition command is used
to tell SD- 10/l 5 whether a character is to be treated as a descender
or not. We’ll get to the command in due time. For now, if your
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