MPE/iX Glossary of Terms and Acronyms (32650-90887)

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Glossary of Terms
digitize To convert a continuous function to one containing a finite number of
discrete levels.
direct access To read from or write to a random access device (usually a disk) by
addressing a specific logical record. Direct record access is not possible on
serial storage media (such as magnetic tapes) since data can only be read
sequentially from the first record (or byte) to the nth record (or byte).
direct connect modem A data communications device. A direct connect modem has a
built-in phone jack, allowing the phone line to be plugged directly into the
modem. The opposite of acoustic modem.
direct memory access (DMA) A technique that allows a periperals device to gain direct
access to the main memory of the computer. This method allows extremely
high data transfer rates.
directory A system table showing in what group or account each file is located, as
well as its disk address, so that it can be accessed. A directory may contain
other information such as size of the file, its creation date, any
modification dates, file creator, or file security information.
DISCFREE An MPE/iX utility supplying information about a system's disk free space,
transient and permanent space, and the volumes total space capacity. The
information is supplied in either a histogram or a condensed format.
Equivalent to the MPE V/E FREE5 utility.
DISCUTIL utility An MPE/iX utility that is used primarily to recover data from disks
that cannot be used by the operating system.
disk A circular plate, coated with material which holds a magnetic charge, used
to store computer data. A disk may be fixed, removable, hard, or flexible.
disk drive A peripheral device that reads information from and writes information to
the disk.
disk failure A disk-related problem that causes a disk to be unavailable for use.
disk file A file stored on disk.
disk I/O The electromechanical process of transferring the code and data that are
stored on disk into main memory.
disk loaded See mounting.
disk pack A set of one or more disk platters stacked inside a plastic cylindrical
container.
disk platter An aluminum disk coated with magnetic material. One or more platters
are mounted on a central spindle, and together they form a complete disk
pack. Information may be recorded on one or both sides of each platter
within the pack.
disk sector A section of a disk's surface (256 contiguous bytes). A file is stored in one
or more sectors.
disk space The space available on a disk to store data.
disk status The state of a disk recognized by the system. See MEMBER, MASTER,