shifting the contents of {HEAD ~ said plurality} of memory locations 2N+1 to 1 to respective ones of {TAIL ~ memory locations} 2N to 0 
shifting the contents of { HEAD ~ said plurality } of memory locations 2N+1 to 1 to respective ones of { TAIL ~ memory locations } 2N to 0
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH