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