Hard disk

main drive of a computer, disk drive which reads and writes to a hard magnetic disk (Computers)

A hard disk drive (HDD), commonly referred to as a hard drive, hard disk or fixed disk drive, is a non-volatile storage device which stores digitally encoded data on rapidly rotating platters with magnetic surfaces. Strictly speaking, "drive" refers to a device distinct from its medium, such as a tape drive and its tape, or a floppy disk drive and its floppy disk. Early HDDs had removable media; however, an HDD today is typically a sealed unit with fixed media.
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Noun
1. a rigid magnetic disk mounted permanently in a drive unit
(synonym) hard disc, fixed disk
(hypernym) magnetic disk, magnetic disc, disk, disc
(hyponym) removable disk
(part-holonym) disk drive, disc drive, hard drive, Winchester drive

A flat, circular, rigid plate with a magnetizable surface on one or both sides of which data can be stored. Note: A hard disk is distinguished from a diskette by virtue of the fact that it is rigid. Early in the development of computer technology, hard disks, often multiple disks mounted on a common spindle, were interchangeable and removable from their drives, which were separate from the processor chassis. This technology is still in use, especially in conjunction with large mainframe computers, but physically smaller computers use hard disks that are in sealed units, along with their control electronics and read/write heads. The sealed units are usually installed permanently in the same chassis that contains the processor.

<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.
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.
(1999-01-07)