The disks are divided into {TAIL ~ sectors} and each sector as {HEAD ~ a symbol} marking printed thereon 
The disks are divided into { TAIL ~ sectors } and each sector as { HEAD ~ a symbol } marking printed thereon
OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH