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184
Glossary
DIMM: Dual Inline Memory Module. A unit of RAM used for memory
expansion.
DIP switch: A set of tiny toggle switches built into a dual in-line
package, which is mounted directly on a circuit board. The switches
may be rocker-style or sliders. In both cases, the tip of a pen or
pencil is required to flip the switch on or off.
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.
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