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value. Some examples will make this clearer. As shown in Figure
9-7, if we add the numbers for the dots that print in a column,
the sum will be a number in the range of 0 to 255. Each number
from O-255 represents a unique combination of dots.
So add up the values of the dots in each column using this
system. In Figure 9-8 we’ve shown our grid with the sums of the
columns filled in across the bottom (see if these agree with your
answers!). Across the top of the grid you’ve probably noticed
the cryptic labeling of each column: ml, m2, m3, etc. These labels
correspond to the labels in the command syntax statement, which
we’ll get to shortly.
m,m,m,m,m,m,m.m,m,m,,m,,
128
~ l
!
;* _~---~~
ASCII Code
64
q-~i ~
Descender
f’-
Start column
End column
M, = Descender * 126 + (Start * 16) + End
Figure 9-8. Add the values of the dots in each column and write the sum
of each column at the bottom.
H Assigning a value to your character
We’ve done a pretty thorough job of designing and describing
a user-defined character. But the SD-lo/l5 has room for 240
download characters-how does it know which user-defined
character we want to print? Exactly the same way it knows which
standard character we want to print: every character is assigned
a unique number.
The standard characters are assigned the ASCII codes-
numbers from 0 to 255. For the download character sets you
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