HP 39gII, User Manual

Page: 267 / 355

Programming 257
commands2 . Continue evaluating tests until a true is
found. If no true test is found, execute commandsD , if
provided.
Example:
CASE
IF THEN RETURN
"negative" ;
END
IF THEN RETURN
"small" ;
END
DEFAULT RETURN
"large" ;
END
;
Drawing
Commands
There are 10 graphic variables in the HP39gII, called G0
to G9 . G0 is always the current screen graphic.
G1 to G9 can be used to store temporary graphic objects
(called GROBs for short) when programming applications
that use graphics. Variables G1 to G9 are temporary and
are cleared when the calculator turns OFF.
They are twenty-six functions that can be used to modify
graphic variables. Thirteen of them work based on
Cartesian coordinates using the Cartesian plane defined
in the current app by the variables Xmin, Xmax, Ymin,
and Ymax in the plot setup menu.
Thirteen of them work on pixel coordinates where the
pixel
0,0
is the top left pixel of the GROB , and
255,126
is the bottom right. This second set of function has a _P
suffix on the function name.
PIXON and
PIXON_P
Syntax:
PIXON
([ G ] , xposition, yposition [ ,color ])
PIXON_P
([ G ], xposition, yposition [ ,color ])
Sets the color of the pixel of G with coordinates x,y to
color. G can be any of the graphic variables and is
optional. The default is G0 , the current graphic. Color
can be
0
to
3
(
0
=black,
1
= dark gray,
2
= light gray,
3
=
white) and is optional. The default is
0
.
PIXOFF and
PIXOFF_P
Syntax:
PIXOFF
([ G ] , xposition, yposition )
PIXOFF_P
([ G ], xposition, yposition )
x 0
<
x 1
<