Then the system reads the data in all the sectors of the disk with a reading routine, and saves {HEAD ~ the data} in {TAIL ~ the free memory space} 
Then the system reads the data in all the sectors of the disk with a reading routine , and saves { HEAD ~ the data } in { TAIL ~ the free memory space }
OTH OTH OTH OTH 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 TAIL TAIL