While receiving a disk drive reading command, {TAIL ~ the system} processes {HEAD ~ the data} saved in the free memory space according to the disk drive reading command 
While receiving a disk drive reading command , { TAIL ~ the system } processes { HEAD ~ the data } saved in the free memory space according to the disk drive reading command
OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH