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ATARI Light Pen Operator's Manual
MODULE B (LINE 9000)
Identical to PENBUF loader described in Section 6. Because of
memory limitation< the loader for the 8K version is different than
the loader discussed in Section 6 (see Appendix G).
MODULE C (LINE 1000)
SETUP initializes color hues (lines lOlOi
1015)/ clears screen (by the
GRAPHICS command)/
marks borders of screen (line 1020) draws menu
field separators (line 1025)/ then draws each menu symbol. Each
statement (1060-1130) corresponds to a new symbol/ and is in the order
in which each symbol appears on the screen. Then using two mode
indicators/ PENMODE and PENCOLR/
it draws the two mode indicator bars
(lines .1171/ 1180). This is accomplished by entering the second half
of the Move Modebar (Module K) subroutine/ which is the part that
draws the new bar. SETUP then executes a BASIC RETURN either to Module
A/ Module P/ or Module R/ which are the only calling routines.
MODULE D (LINE 950)
Use RESUMODE to reenter a drawing mode once it has been exited to
either change the color mode or to perform one of the three functions.
The variable PENMODE indicates which
mode to enter.
The color modes
and drawing modes are explained earlier in this section.
MODULE E (LINE 150)
Enter ELASTIC mode/ which is drawing mode 1 (PENM0DE=1). ELASTIC mode
first gets an origin or pivot point (defined by the coordinates XP/
YP) and then enters a loop in which the old line is erased (line 190)
and a line to the new point is drawn (line 210). As long as the pen is
down/ this loop is repeated (line 230). If the pen is lifted and then
set down again/ a new pivot point is defined/ and the loop entered
(line 240). As with all the drawing modes/ it exits at line 2048 of
the GETPOS call (Module
I).
MODULE F (LINE 300)
Enter FILL mode/ drawing mode 2 (PENM0DE=2). First a preliminary point
is fetched and plotted. A loop is then entered which does a FILL
command (see ATARI BASIC Reference Manual for more information on
this command) from the last point plotted to the current pen position.
As with all the drawing modes/
it is exited at 2048 in Module I.
ATARI Light Pen Demonstration Program Cassette — 25
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