{HEAD ~ An IOM} tracks {TAIL ~ the order} of instruction execution through the pipeline—that is, which instructions are older or newer than a given instruction—by maintaining representations of instructions in true program order, such as in a circular buffer, FIFO, or the like 
tracks
{ HEAD ~ An IOM } tracks { TAIL ~ the order } of instruction execution through the pipeline — that is , which instructions are older or newer than a given instruction — by maintaining representations of instructions in true program order , such as in a circular buffer , FIFO , or the like
HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH