The OTFOC patch

THE 'OPENTYPE FILE OPEN/CLOSE' ROUTINE
This routine opens or closes an opentype file according to the contents of
the A register. When it holds 0 a "D" channel is attached to the stream
given in the DFCA. A non zero value closes the corresponding stream. This
routine was added in System 3d.

0287 OTFOC      AND  A
0288            JP   Z,#1261,OPEN_CHAN   Open a channel if A holds zero.
028B            JP   #140C,CLOSE_STRM    Otherwise close the stream.