Specifications
Glossary
5
wires to communicate digitally at high speed
between the telephone company central office
(CO) and the subscriber. ADSL sends information
asymmetrically, meaning it is faster one way than
the other. The original ADSL speed was T-1
(1.536Mbps) downstream from the carrier to the
subscriber’s premises and 16Kbps upstream.
However, ADSL is available in a variety of configu-
rations and speeds. See also DSL.
Advanced Encryption Standard (AES) A
128-bit block data encryption standard often used
to encrypt traffic in secure wireless networks.
AdvancedTCA Advanced Telecom Computing
Architecture is a new series of standards for telecom
processor blades and chassis. It is also known as the
PICMG 3.0 specification. See also PICMG.
AGP (accelerated graphics port) Developed
by Intel, AGP is a fast, dedicated interface between
the video adapter or chipset and the motherboard
chipset North Bridge. AGP is 32 bits wide; runs at
66MHz base speed; and can transfer 1, 2, 4, or 8
bits per cycle (1x, 2x, 4x, or 8x modes) for a
throughput of up to 2132MBps. AGP has been
replaced by PCI Express in newer systems.
aliasing Undesirable visual effects (sometimes
called artifacts) in computer-generated images
caused by inadequate sampling techniques. The
most common effect is jagged edges along diagonal
or curved object boundaries. See also antialiasing.
allocation unit See cluster.
alphanumeric characters A character set that
contains only letters (A–Z) and digits (0–9). Other
characters, such as punctuation marks, also might
be allowed.
AMD Short for Advanced Micro Devices, the
number-two PC processor maker. AMD makes the
popular K6, Athlon, Opteron, and Duron series of
processors, as well as chipsets and flash memory
devices.
AMD64 AMD-developed 64-bit extensions to the
standard IA-32 system architecture (originally
known as x86-64). Supported by AMD Opteron,
Athlon 64, and other AMD 64-bit processors.
ampere The basic unit for measuring electrical
current. Also called amp.
ampere hour (Ah) A current of one ampere
flowing for one hour. Often used to indicate the
storage capacity of a rechargeable battery.
AMR Short for Audio/Modem Riser, AMR is an
Intel-developed specification for packaging modem
I/O ports and a codec chip into a small card that
can be installed into an AMR slot on a mother-
board. Although many motherboards have AMR
slots, AMR risers have not been popular, and the
CNR specification has largely replaced AMR. See
also CNR.
analog The representation of numerical values
by physical variables such as voltage, current, and
so on; continuously variable quantities whose
values correspond to the quantitative magnitude of
the variables.
analog loopback A modem self-test in which
data from the keyboard is sent to the modem’s
transmitter, modulated into analog form, looped
back to the receiver, demodulated into digital form,
and returned to the screen for verification.
analog signals Continuously variable signals.
Analog circuits are more subject to distortion and
noise than are digital circuits but are capable of
handling complex signals with relatively simple
circuitry. See also digital signals.
analog-to-digital converter An electronic
device that converts analog signals to digital form.
AND A logic operator having the property that if
P is a statement, Q is a statement, and R is a state-
ment, then the AND of P, Q, R is true if all state-
ments are true and is false if any statement is false.
AND gate A logic gate in which the output is 1
only if all inputs are 1.
animation The process of displaying a sequen-
tial series of still images to achieve a motion effect.
ANSI (American National Standards
Institute) A nongovernmental organization
founded in 1918 to propose, modify, approve, and
publish data-processing standards for voluntary use
in the United States. It’s also the U.S. representative
to the International Standards Organization (ISO) in
Paris and the International Electrotechnical Com-
mission (IEC). Contact ANSI at 1430 Broadway, New
York, NY 10018.
Appendix A
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