Appropriate registers are provided to store {HEAD ~ the numbers} which represent the subtrahend and minuend of {TAIL ~ a subtraction operation} 
Appropriate registers are provided to store { HEAD ~ the numbers } which represent the subtrahend and minuend of { TAIL ~ a subtraction operation }
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL