AT&T 6300 Programmer's Manual page 326

LINE
Statement
7-170
Each time LINE plots a pixel on the screen, it
will use the current circulating bit in "style."
If that bit is 0, no pixel is plotted. If the bit is a
1, then a pixel is plotted. After each pixel, the
next bit position in "style" is selected.
Since a
°
bit in "style" does not clear out the
old contents, the user may wish to draw a
background line before a "styled" line in order
to force a known background.
"Style" is used for normal lines and boxes, but
has no effect on filled boxes.
LINE (0,0)-(160,1 00),3,,&HFFOO
The example above draws a dashed line from
the upper left hand corner to the screen center.