AT&T 6300 Programmer's Manual page 393

PAINT
Statement
The structure of the string expression appears
as follows:
x increases
bit of tile byte
x.y 8 7 6 5 4 3 2 1
0,0
Ixlxlxlxlxlxlxlx
Tile byte 0
0,1
Ixlxlxlxlxlxlxlx
Tile byte 1
0,2
Ixlxlxlxlxlxlxlx
Tile byte 2
0,63
Ixlxlxlxlxlxlxlx
Tile byte 63 (maximum allowed)
The tile pattern is replicated uniformly over
the entire screen.
Each byte in the tile string masks 8 bits along
the x axis when plotting points. Each byte of
the tile string is rotated as required to align
the y axis such that:
Since there is only one bit per pixel in high-
and super-resolution modes (SCREEN 2 and
3), a point is plotted at every position in the bit
mask which has a value of
1.
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