Processing from {HEAD ~ either process block} 1140 or {TAIL ~ process block} 1150 terminates at END block 1155 
Processing from { HEAD ~ either process block } 1140 or { TAIL ~ process block } 1150 terminates at END block 1155
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH