Tandy 1000 Basic Reference Manual page 285

Chapter 10 I BASIC Keywords
PRESET produces a n opposite image on the screen. With 2
color sets, white becomes black on the screen. With 4 and
16 color sets, the color value becomes the numeric opposite
on the screen. This table shows the color displayed for each
possible value:
16 color
4 color
Array Screen Array Screen
Value Color Value Color
0 3 0 15
1 2 1 14
2
1
2 13
3 0 3 12
4 11
5 10
6 9
7
8
8
7
9
6
10 5
11 4
12 3
13 2
14
1
15 0
AND transfers the image over existing image. The result is
a logical AND of the array and the image on the screen.
OR superimposes a n image onto an existing image. The re-
sult is a logical
OR
of the array and the image on the
screen.
XOR inverts the points on the screen where a point exists
in the array image. When a n image is PUT against a com-
plex background twice, the background is restored
un-
changed. This lets you move an object around the screen
without obliterating the background.
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