replacing the current value in {HEAD ~ the virtual type} with {TAIL ~ the new value} identified in the instruction string using a process embodied in the computer program 
replacing the current value in { HEAD ~ the virtual type } with { TAIL ~ the new value } identified in the instruction string using a process embodied in the computer program
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH