Epson 10020 - Manual (Page 48)

stored. Double-density diskettes have either 40 or 80 tracks,
and high-density diskettes have 80 tracks. The double-density,
360KB diskettes you use in your Apex have 40 tracks.
A hard disk consists of two or more platters stacked on top of
one another; so it has four or more sides with many more tracks
per side than a diskette.
A disk is further divided by sectors. To understand what a
sector is, picture the spokes on a bicycle wheel radiating from
the center of the wheel to the tire. The space between one
spoke and the next is like a sector on a diskette. (See the figure
below.) The diskettes you use on the Apex have 9 sectors per
track; other types of diskettes can have 8, 15, or 18 sectors. The
number of sectors on a hard disk depends on the type of hard
disk.
Using Your Computer 2-7