Specifications
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Appendix A Glossary
DOCSIS See CableLabs Certified Cable Modem.
doping Adding chemical impurities to silicon
(which is naturally a nonconductor) to create a
material with semiconductor properties that is then
used in the manufacturing of electronic chips.
DoS (denial of service) An Internet attack on a
resource that prevents users from accessing email,
websites, or other services. It usually exploits secu-
rity shortcomings in email or web servers. See also
DDoS.
DOS (Disk Operating System) A collection of
programs stored on the DOS disk that contain rou-
tines enabling the system and user to manage
information and the hardware resources of the
computer. DOS must be loaded into the computer
before other programs can be started.
dot pitch A measurement of the width of the
dots that make up a pixel. The smaller the dot
pitch, the sharper the image.
dot-matrix printer An impact printer that
prints characters composed of dots. Characters are
printed one at a time by pressing the ends of
selected wires against an inked ribbon and paper.
dots per inch (dpi) A measure of resolution
used primarily for printers and scanners.
double-conversion online UPS An advanced
UPS design that converts AC power to DC for UPS
battery charging and then back to AC. This type of
UPS provides excellent power conditioning and
supports long run times and multiple servers with a
single unit.
double density (DD) An indication of the stor-
age capacity of a floppy drive or disk in which
eight or nine sectors per track are recorded using
MFM encoding. See also MFM encoding.
download The process of receiving files from
another computer.
downtime Operating time lost because of a
computer malfunction.
DPMI (DOS Protected Mode Interface) An
industry-standard interface that allows DOS appli-
cations to execute program code in the protected
mode of the 286 or later Intel processor. The DPMI
specification is available from Intel.
DPMS (Display Power Management
Signaling) A VESA standard for signaling a
monitor or display to switch into energy conserva-
tion mode. DPMS provides for two low-energy
modes: standby and suspend.
DRAM (dynamic random access memory)
The most common type of computer memory,
DRAM can be manufactured very inexpensively
compared to other types of memory. DRAM chips
are small and inexpensive because they normally
require only one transistor and a capacitor to repre-
sent each bit. The capacitors must be energized
every 15ms or so (hundreds of times per second) to
maintain their charges. DRAM is volatile, meaning
it loses data with no power or without regular
refresh cycles.
drive A mechanical device that manipulates data
storage media.
driver A program designed to interface a particu-
lar piece of hardware to an operating system or
other standard software.
drum The cylindrical photoreceptor in a laser
printer that receives the document image from the
laser and applies it to the page as it slowly rotates.
DSL (digital subscriber line) A high-speed
digital modem technology. DSL is either symmetric
or asymmetric. Asymmetric provides faster down-
stream speeds, which is suited for Internet usage
and video on demand. Symmetric provides the
same rate coming and going. See also ADSL.
DSM (digital storage media) A digital storage
or transmission device or system.
DSP (digital signal processor) Dedicated,
limited-function processor often found in modems,
sound cards, cellular phones, and so on.
DTE (data terminal [or terminating] equip-
ment) The device, usually a computer or termi-
nal, that generates or is the final destination of
data. See also DCE.
dual cavity pin grid array Chip packaging
designed by Intel for use with the Pentium Pro
processor that houses the processor die in one
cavity of the package and the L2 cache memory in
a second cavity within the same package.
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