and indicate the position directed by the contents of {HEAD ~ the IMA counter} to represent the position of {TAIL ~ the present cursor} 
and indicate the position directed by the contents of { HEAD ~ the IMA counter } to represent the position of { TAIL ~ the present cursor }
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL