In {HEAD ~ alternative}, such code can be interpreted by the CUI 18 as {TAIL ~ a new microinstruction} 
In { HEAD ~ alternative } , such code can be interpreted by the CUI 18 as { TAIL ~ a new microinstruction }
OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL