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But there is another area of *memory in the SD- lo/ 15 reserved
for user-defined characters. These are characters that you design
and download into SD-10/15. When download characters are
defined they are stored in RAM (random access memory), which
allows you to define or modify them at any time.
Each of these characters, whether it is from the standard
character ROM or in download RAM, is constructed on a grid
which is six “boxes” wide by nine “boxes” high. The dots used
to print a character can be inside any of the boxes. In addition,
a dot can straddle any of the vertical lines. As an example, take
a look at the enlarged “9” superimposed on the grid in Figure
9-3. As you can see, some dots are inside the boxes, and some
are centered on the vertical lines. This, in effect, makes the
character grid 11 dots wide by 9 dots high. To see how the rest
of the characters in the standard character ROM are constructed,
take a look at Appendix C.
Figure 9-3. Dots can be inside boxes or straddle the vertical lines of the
grid.
DEFINING YOUR OWN CHARACTERS
You’ve seen how the engineers at Star designed their characters
by using a grid to lay out the dots. Now you can define characters
exactly the same way. Make up some grids (photocopy Figure
9-4 if you wish) and get ready to be creative! (Just in case you
are not feeling creative, and to make our explanations a little
clearer, we’ll be using a picture of a chemist’s flask as an example
of a download character. You can see how we’ve laid it out in
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