The computer program is modified while {TAIL ~ the computer program} is executed by {HEAD ~ the processor unit} 
The computer program is modified while { TAIL ~ the computer program } is executed by { HEAD ~ the processor unit }
OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD