If the processing of {HEAD ~ block} 1210 evaluates to “false”, then the head and tail pointers point to {TAIL ~ the same node}, but the DPQ 300 is not null 
If the processing of { HEAD ~ block } 1210 evaluates to “ false ” , then the head and tail pointers point to { TAIL ~ the same node } , but the DPQ 300 is not null
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH