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ATARI Light Pen Operator's Manual
from languages other than BASIC>
no such stack value utill occur.
Thus the "PLA" instruction must be deleted if you are not using
BASIC.
3.
Sense a switch closure on the pen by reading locations 632» 633»
634i or 635i
depending on whether the pen is plugged into jack #1
2» 3i or 4. The pen may be used in a jack other than
jack #1 by using the following locations;
Location
Jack
632
1
633
2
634
3
635
4
4.
When you call PENBUF as a subroutine, the X and Y values will be
returned to the locations shown above. It is up to you to
determine the correspondence between your plot coordinate system
in this other language and the 160 by 96 (GRAPHICS 23) or 40 by
24 (GRAPHICS 0) of ATARI BASIC.
General Programming Notes - 64
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