Epson Apex 20020 - Manual (Page 59)

Unlike a diskette, a hard disk is rigid and fixed in place. It is
sealed in a protective case to keep it free from dust and dirt. A
hard disk stores data the same way that a diskette does, but it
works faster and has a much larger storage capacity.
All disks are divided into data storage compartments by sides,
tracks, and sectors. Double-sided diskettes-like the ones you
use in your computer-store data on both sides. On your disk
there are concentric rings, called tracks, in which a disk can
store data. Double-density diskettes (such as 360KB diskettes)
have 40 tracks, and high-density diskettes (such as 1.2MB
diskettes) have 80 tracks.
A hard disk consists of two or more magnetically-coated
platters stacked on top of one another, so it has four or more
sides with many more tracks 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.) Each track on a 1.2MB diskette has 15 sectors, and
each sector holds 512 bytes.
Using Your Computer 3-7