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GLOSSARY
GL – 2
CONTROLLERCONTROLLER
CONTROLLERCONTROLLER
CONTROLLER
A miniature CPU dedicated to controlling a peripheral device, such
as a disk drive, tape drive, video display terminal, or printer. The
controller executes commands from the central processing unit and
reissues commands to the peripheral device.
CORRECTABLE ERRORCORRECTABLE ERROR
CORRECTABLE ERRORCORRECTABLE ERROR
CORRECTABLE ERROR
An error that can be overcome by the use of Error Detection and
Correction.
CYLINDERCYLINDER
CYLINDERCYLINDER
CYLINDER
On several disk surfaces sharing a common rotational axis, the
aggregate of tracks at a given radial position. A set of disk tracks
that are simultaneously under the set of read/write heads. This
three-dimensional storage volume can be accessed after a single
seek.
CYLINDER ZEROCYLINDER ZERO
CYLINDER ZEROCYLINDER ZERO
CYLINDER ZERO
The outermost cylinder in a drive that can be used for data storage.
DD
DD
D
DATADATA
DATADATA
DATA
An ordered collection of information. In a specific case, it is the
information processed by a computer.
DATA SEPARATORDATA SEPARATOR
DATA SEPARATORDATA SEPARATOR
DATA SEPARATOR
An electronic circuit which decodes playback data and produces
separate clock and data bits. Sometimes incorrectly used to denote
data synchronizer.
DATA SYNCHRONIZERDATA SYNCHRONIZER
DATA SYNCHRONIZERDATA SYNCHRONIZER
DATA SYNCHRONIZER
An electronic circuit producing a clock signal that is synchronous
with the incoming data stream. This clock signal is then used to
decode the recording code being used into user data.
DATA TRANSFER RATEDATA TRANSFER RATE
DATA TRANSFER RATEDATA TRANSFER RATE
DATA TRANSFER RATE
In a disk or tape drive, the rate at which data is transferred to or
from the storage media. It is usually given in thousands of bits per
second (Kbit/second) or millions of bits per second (Mbit/second).
DEDICATED LANDING ZONEDEDICATED LANDING ZONE
DEDICATED LANDING ZONEDEDICATED LANDING ZONE
DEDICATED LANDING ZONE
A designated radial zone on the disk where contact starting and
stopping occur by design.
DEDICATED SERVODEDICATED SERVO
DEDICATED SERVODEDICATED SERVO
DEDICATED SERVO
A servo scheme in which a prerecorded pattern on an otherwise
unused disk surface provides position information to the servo
circuitry by means of a head reading that surface.
DEFECTDEFECT
DEFECTDEFECT
DEFECT
A magnetic imperfection in a recording surface.
DEFECT MANAGEMENTDEFECT MANAGEMENT
DEFECT MANAGEMENTDEFECT MANAGEMENT
DEFECT MANAGEMENT
A general methodology of avoiding data errors on a recording
surface by avoiding the use of known bad areas of media. Usually
defective sectors or tracks are retired and data are written in
alternate locations. Several algorithms are possible such as “sector
slipping,” or “spare sector per track.”
DEFECT MAPDEFECT MAP
DEFECT MAPDEFECT MAP
DEFECT MAP
A list of defects that fall within a pass/fail criteria of a user. This list
is usually used by an operating system or a disk drive controller for
defect management.
DEFECT SKIPPINGDEFECT SKIPPING
DEFECT SKIPPINGDEFECT SKIPPING
DEFECT SKIPPING
A defect management scheme for avoiding surface defects. It has
data written before and after the defect, instead of using alternate
tracks or sectors to avoid use of the defective area.
DENSITYDENSITY
DENSITYDENSITY
DENSITY
Generally, recording density. See areal, bit, and storage density.
DC ERASEDC ERASE
DC ERASEDC ERASE
DC ERASE
The method of erasing a track using a DC write/erase current
through either a Read/Write or Erase head.
DIGITALDIGITAL
DIGITALDIGITAL
DIGITAL
Any system that processes digital binary signals (having only values
of a 1 or 0; usually in bits and bytes) rather than analog signals
(signals that can have many values)
DIGITAL MAGNETIC RECORDINGDIGITAL MAGNETIC RECORDING
DIGITAL MAGNETIC RECORDINGDIGITAL MAGNETIC RECORDING
DIGITAL MAGNETIC RECORDING
See magnetic recording.
DIRECT ACCESSDIRECT ACCESS
DIRECT ACCESSDIRECT ACCESS
DIRECT ACCESS
Access directly to memory location. (See random access).
DIRECT MEMORY ACCESSDIRECT MEMORY ACCESS
DIRECT MEMORY ACCESSDIRECT MEMORY ACCESS
DIRECT MEMORY ACCESS
A mean of data transfer between the device and host memory
without processor intervention.
DIRECTORYDIRECTORY
DIRECTORYDIRECTORY
DIRECTORY
A listing of files maintained by the disk operation system (DOS) or a
data base management system to enable a user to quickly access
data files.
DISKDISK
DISKDISK
DISK
A flat, circular piece of metal (usually aluminum) or plastic (usually
mylar) with a magnetic coating upon which information can be
recorded. (See, for example, floppy disk or Winchester disk)
DISK DRIVE OR DISK MEMORY DEVICEDISK DRIVE OR DISK MEMORY DEVICE
DISK DRIVE OR DISK MEMORY DEVICEDISK DRIVE OR DISK MEMORY DEVICE
DISK DRIVE OR DISK MEMORY DEVICE
The total electromechanical storage device containing disks and
read/write heads, head positioning mechanism, drive motor, and
electronics.
DISK PACKDISK PACK
DISK PACKDISK PACK
DISK PACK
A number of metal disks packaged in a canister for removal from the
disk drive (predecessor of Winchester technology).
DISK OPERATING SYSTEM (DOS)DISK OPERATING SYSTEM (DOS)
DISK OPERATING SYSTEM (DOS)DISK OPERATING SYSTEM (DOS)
DISK OPERATING SYSTEM (DOS)
The master computer system program that schedules tasks,
allocates the computer system resources, controls accesses to
mass storage devices, manages files, and so forth. Typical disk
operating systems include CP/M, MS-DOS, and UNIX.
DISK STORAGEDISK STORAGE
DISK STORAGEDISK STORAGE
DISK STORAGE
Auxiliary memory system containing disk drives.
DISK TRANSFER RATEDISK TRANSFER RATE
DISK TRANSFER RATEDISK TRANSFER RATE
DISK TRANSFER RATE
The rate that digital data is transferred from one point to another.
Expressed in either bits/second or bytes/second.
DOUBLE FREQUENCY ENCODINGDOUBLE FREQUENCY ENCODING
DOUBLE FREQUENCY ENCODINGDOUBLE FREQUENCY ENCODING
DOUBLE FREQUENCY ENCODING
Another name for FM encoding. This is because all possible data
combinations will result in only two possible temporal displacements
of adjacent data bits, specifically “1F” and 2F.”
EE
EE
E
EARLY WINDOWEARLY WINDOW
EARLY WINDOWEARLY WINDOW
EARLY WINDOW
A data window that has been intentionally shifted in time in an early
direction.
EMBEDDED SERVOEMBEDDED SERVO
EMBEDDED SERVOEMBEDDED SERVO
EMBEDDED SERVO
A servo technique used for track following. Position information is
prerecorded between data areas in a track so that a data head, and
proper additional circuitry, can determine the data head location
with respect to the center position of the track (or cylinder) in
question.
ERASEERASE
ERASEERASE
ERASE
A process by which a signal recorded on a medium is removed and
the medium made ready for rerecording.
ERROR CORRECTION CODE (ECC)ERROR CORRECTION CODE (ECC)
ERROR CORRECTION CODE (ECC)ERROR CORRECTION CODE (ECC)
ERROR CORRECTION CODE (ECC)
A mathematical algorithm that can detect and correct errors in a
data field. This is accomplished with the aid of Check Bits added to
the raw data.
ERROR FREEERROR FREE
ERROR FREEERROR FREE
ERROR FREE
A recording surface that has no defects.
ERROR RATEERROR RATE
ERROR RATEERROR RATE
ERROR RATE
The number of errors (type must be specified) that occur in a
specified number of bits read.
ERROR RECOVERY PROCEDUREERROR RECOVERY PROCEDURE
ERROR RECOVERY PROCEDUREERROR RECOVERY PROCEDURE
ERROR RECOVERY PROCEDURE
The process that occurs in response to a data error. In a drive
without ECC, this would include re-calibration and re-seeking to the
specified track and rereading the specified data.