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