The disk drive provides a non volatile backup for the random access memory by transferring data between {HEAD ~ the disk drive} and random access memory automatically, or by command, on {TAIL ~ a non realtime basis} 
The disk drive provides a non volatile backup for the random access memory by transferring data between { HEAD ~ the disk drive } and random access memory automatically , or by command , on { TAIL ~ a non realtime basis }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH 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 TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL