< 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)