The subtrahend is stored in the A register and {HEAD ~ the minuend} in {TAIL ~ the B} register 
in
The subtrahend is stored in the A register and { HEAD ~ the minuend } in { TAIL ~ the B } register
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH