AT&T 6300 Programmer's Manual page 510

WINDOW
Statement
7-354
For example if:
WINDOW [-1,-1)-[1,1)
was executed then the screen appears as:
-1,1 0,1 1,1
/1\
y increases
I
I
0,0
I
I
\1/
Y decreases
-1,-1 0,-1 1,-1
Note now that the "y" coordinate is inverted
so that (xl,yl) is the lower-left coordinate and
(x2,y2) is the upper-right coordinate.
If the SCREEN attribute is included then, the
coordinates are not inverted. So that, (xl,yl) is
the upper-left coordinate and (x2,y2) is the
lower-right coordinate.