hard disk definition
<storage> (In contrast to floppy disk). One or more rigid
magnetic disks rotating about a central axle with associated
read/write heads and electronics, used to store data. Most
hard disks are permanently connected to the drive (fixed
disks) though there are also removable disks.
High speed disks have an access time of 28 milliseconds or
less, and low-speed disks run 65 milliseconds or more. The
higher speed disks also transfer their data faster than the
slower speed units.
Each surface of each disk is divided into a number of evenly
spaced concentric circular tracks. The set of all tracks at
a given radius on all surfaces (the tracks which can be
accessed without moving the heads) are known as a cylinder.
Each track is divided into sectors.
The heads "float" just above the disk's surface on a current
of air. As the disk turns it moves the air around it, creaing
theair current. The head has an aerodynamic shape so the
current pushes it away from the disk. A small spring pushes
the head towards the disk at the same time keeping the head at
a constant distance from the disk (about two microns).
Disk drives are commonly characterised by the kind of
interface used to connect to the computer, e.g. ATA, IDE,
SCSI.
See also winchester.
Suchanka's PC-DISK library.
(2004-06-17)
Nearby terms:
hard boot « hard-coded « hardcopy « hard disk » hard disk drive » hard drive » hard link
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