Radio Shack TRS-80 Operation Manual page 44

Computer Graphics
Operation Manual
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PRESET
Sets Pixel OFF (or ON)
PRESET sets a pixel either OFF (~) or ON (1), depending on
switch. If switch is not specified,
~
(OFF) is used.
Values for (~) that are larger than the parameters of
the screen (i.e., greater than 639 for ~ and 239 for
y)
are accepted, but these points are off the screen and
therefore are not PRESET.
Note: The only choice for switch is ~ or 1. If you enter
any other number, an Illegal Function Call error will
result.
Examples
l~
PRESET
(5~,5~),1
2~
PRESET
(5~,5~),~
Turns ON the pixel located at the specified coordinates (in
line
l~)
and turns the pixel OFF (in line
2~).
l~
PRESET
(32~,12~),1
2~
PRESET
(3~~,1~~),1
3~
PRESET
(34~,14~),1
4~
FOR 1=1 TO
l~~~:
NEXT I
5~
PRESET
(32~,12~)
6~
PRESET
(3~~,1~~)
7~ PRESET (34~,14~)
8~
FOR 1=1 TO
l~~~:
NEXT I
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