From HomoExcelsior

1. A device that reads data stored on a disk and may write data onto the disk for persistent storage.  2. Hard Disk Drive.

Disk drives are generally magnetic or optical and write to a circular disk, which may be hard or flexible (floppy), which spins a high rate. Disk drives are single air-tight enclosure with multiple platters of disks inside, each read (and written) by disk heads which move between the center of the disk to the outer edge. When the heads are not in use then are left in a position called the landing zone.

See also: CDRom Drive.

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