GLOSSARY
Glossary
A
access
To obtain data from, or place data into, RAM, a register, or data storage device.
access time
The interval between the issuing of an access command and the instant that the target data may be read or written. Access time includes seek time, latency and controller overhead time.
address
A number, generally binary, distinguishing a specific member of an ordered set of locations. In disk engineering, the address may consist of drives (unit address), radial positions (cylinder address), or circumferential position (sector address).
allocation
A process of assigning designated areas of the disk to particular files.
alternate track
A spare track used in the event that a normal track becomes damaged or is unusable.
analog
A signal or system that does not use digital states to convey information. A signal may have any number of significant states (values), contrasted to digital signals which can only have two states.
ANSI
American National Standards Institute.
application program
A sequence of programmed instructions that tell the computer how to perform some
areal density
Bit density (bits per inch) multiplied by track density (tracks per inch) or bits per square inch.
asymmetry
A distortion of the readback signal which is shown in different intervals between the positive and negative voltage peaks.
auxiliary memory
Memory other than main memory; generally a mass- storage subsystem containing disk drives and backup tape drives, controller(s) and buffer memory (also called peripheral memory).
average access time
The average time to make all possible length accesses (seeks).
average seek time
The average time to make all possible length seeks. A typical measure of performance.
B
bad block
A block that cannot store data because of a media flaw.
bit
An abbreviation for binary digit, of which there are two (0 and 1). A bit is the basic data unit of most digital computers. A bit is usually part of a data byte or word, but bits may be used singly to control or read logic “on- off” functions. The fundamental unit information, often used loosely to refer to a circuit or magnetization state at a particular instant in time.
BIOS
Acronym for Basic Input/Output System. The firmware area of a CPU that controls operations through the system bus and to the attached cards and peripheral devices.
BPI
Acronym for bits per inch. See bit density.
block
A group of bytes handled, stored, and accessed as a logical data unit, such as an individual file record.
buffer
A temporary data storage area that compensates for a difference in data transfer rates and/or data processing rates between sender and receiver.
bus
A collection of functionally parallel conductors that forms an interconnection between functional blocks in a digital device. A length of parallel conductors that forms a major interconnection route between the computer system CPU (central processing unit) and its peripheral subsystems. Depending on its design, a bus may carry data, addresses, power, and more.
byte
An ordered collection of bits treated as a unit. Most often, a byte is understood to consist of eight bits. One byte is necessary to define an alphanumeric character.
C
cache
Random access memory (RAM) used as a buffer between the CPU and the disk drive.
capacity
The amount of data, usually expressed in bytes, which can be stored in a given device or portion of same.
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