In the present specification, the term operating system will be employed to refer generally to {HEAD ~ operating systems} of {TAIL ~ this class} 
of
In the present specification , the term operating system will be employed to refer generally to { HEAD ~ operating systems } of { TAIL ~ this class }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL