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Direct Memory Access (DMA): A dedicated channel that bypasses the Central
Processing Unit (CPU) and enables a device to access memory directly. If two
devices use the same DMA channel, the data required by one device
overwrites the data required by the other—this is one type of hardware conflict.
To resolve the conflict, you must reassign one of the devices to a vacant DMA
channel.
directory: See folder.
disable: To turn a computer option off. In a menu or dialog box, a disabled option appears
dim (or "grayed out") and clicking it has no effect. See also enable.
disc: An optical storage medium for computer information. It consists of a shiny, non-
magnetic metal platter on which information is recorded and read back using
laser technology. See also CD-ROM.
disk: (1) The general term for any circular platter that can store computer information. (2)
A magnetic storage medium, such as a hard disk or diskette. It consists of a
platter or set of platters coated with a magnetic material and enclosed inside a
protective case. See also CD-ROM, hard disk, diskette.
disk cache: A technique that speeds up processing. Each time your application receives
data from a disk, a special program stores the data in a reserved area of
memory (RAM). When the application next requests data, it looks for it first in
the disk cache. Since reading from and writing to memory is quicker than using
a disk drive, this can considerably improve system performance.
disk drive: The device that reads and writes information and programs on a diskette or
hard disk. It rotates the disk at high speed past one or more read/write heads.
diskette: A thin, flexible diskette in a protective jacket that stores magnetically encoded
information. Diskettes can be removed from the computer and come in two
sizes: 5.25-inch and 3.5-inch. The server uses 3.5-inch diskettes.
disk mirroring: A technique in which the contents of a hard disk are duplicated on other
hard disk(s) to protect against data loss. Any changes made to the contents of
the original disk are simultaneously applied to the other disk(s).
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