Radio Shack TRS-80 Operation Manual page 43

Computer Graphics Operation Manual
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Reads and prints the value of the pixel at the point's
coordinates (3~~,1~~) and displays its value: 1.
PRINT
&POINT(3~~~,1~~~)
Since the pixel is off the screen, a -1 is returned.
PRINT
&POINT(-3~~~,-1~~~)
Since the pixel is off the screen, a -1 is returned.
PSET (
2~~
,
l~~)
,11
PRINT
&POINT(2~~,1~~)
Reads and prints the value of the pixel at the point's
coordinates (2~~,1~~) and displays its value:
11.
l~ PSET(3~~,1~~),1
2~
IF &POINT
(3~~, l~~
)=1 THEN PRINT "GRAPHICS BASIC!"
Sets the point ON. Since the point's value is 1, line
2~
is
executed and Graphics BASIC is displayed:
GRAPHICS BASIC!
5 SCREEN ~
l~ PSET(RND(64~),RND(24~»,1
2~
IF
&POINT(32~,12~)=1
THEN STOP
3~
GOTO
l~
Sets points randomly until
(32~,12~)
is set.
5 CLR
l~ LINE(5~,8~)-(12~,l~~),1,BF
2~
PRINT
&POINT(1~~,8~)
3~
PRINT
&POINT(11~,8~)
4~
PRINT
&POINT(115,9~)
5~
PRINT
&POINT(5~,4~)
6~
PRINT
&POINT(13~,12~)
The first three pixels are in the filled box, so the value 1
(one) is displayed for each of the statements in lines
2~,
3~,
and
4~.
The pixels specified in lines
5~
and
6~
are not
in the shaded box and ~s are returned.
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