An Early List of Computer Terms - NetLingo The Internet Dictionary: Online Dictionary of Computer and Internet Terms, Acronyms, Text Messaging, Smileys ;-)

An Early List of Computer Terms

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A 

AC-3 (audio coding 3) Dolby's digital audio data compression algorithm adopted for HDTV transmission and used in laserdiscs and
CDs for 5.1 multichannel home theater use. Competes with DTS Zeta Digital. The terms AC-1 and AC-2 are other versions
developed by Dolby for different applications. 

acquisition time The time required for a sample-and-hold (S/H) circuit to capture an input analog value; specifically, the time for
the S/H output to approximately equal its input. 

active equalizer A variable equalizer requiring power to operate. Available in many different configurations and designs. Favored
for low cost, small size, light weight, loading indifference, good isolation (high input and low output impedances), gain availability
(signal boosting possible), and line-driving ability. Disliked for increased noise performance, limited dynamic range, reduced reliability,
and RFI susceptibility; however, used everywhere. 

adaptive delta modulation (ADM) A variation of delta modulation in which the step size may vary from sample to sample. 

ADAT (Alesis digital audio tape) Digital tape recording system developed by Alesis, and since licensed to Fostex & Panasonic,
putting 8-tracks of 16-bit, 44.1kHz digital audio on S-VHS tape. 

ADAT ODI (optical digital interface) See ADAT Optical. 

ADAT Optical Alesis's proprietary multichannel optical (fiber optic) digital interface specification for their family of ADAT
modular digital multitrack recorders. This standard describes transmission of 8-channels of digital audio data through a single fiber
optic cable. 

ADC (or A/D, analog-to-digital converter) The electronic component which converts the instantaneous value of an analog input
signal to a digital word (represented as a binary number) for digital signal processing. The ADC is the first link in the digital chain of
signal processing. 

ADPCM (adaptive differential pulse code modulation) A very fast data compression algorithm based on the differences
occurring between two samples. 

AES (Audio Engineering Society) Founded in 1949, the largest professional organization for electronic engineers and all others
actively involved in audio engineering. Primarily concerned with education and standardization. 

AES-24 An AES standard for sound system control using a computer network to control audio equipment. Formerly called "SC-10"
(after the working group's subcommittee number), the title is Application protocol for controlling and monitoring audio systems
and is broken down into several parts, each issued separately. To date only Part 1: architecture is released; the remaining parts (at
least three) are in process. 

AES/EBU interface The serial transmission format standardized for professional digital audio signals (AES3-1992 AES
Recommended Practice for Digital Audio Engineering - Serial Transmission Format for Two-Channel Linearly Represented
Digital Audio Data) A specification using time division multiplex for data, and balanced line drivers to transmit two channels of
digital audio data on a single twisted-pair cable using 3-pin (XLR) connectors. Issued as ANSI S4.40-1985 by the American
National Standards Institute. In addition, information documents are being prepared describing the transmission of AES3 formatted
data by unbalanced coaxial cable and by fiber optic cable. 

algorithm A structured set of instructions and operations tailored to accomplish a signal processing task. For example, a fast Fourier
transform (FFT), or a finite impulse response (FIR) filter are common DSP algorithms. 

aliasing The problem of unwanted frequencies created when sampling a signal of a frequency higher than half the sampling rate.
See: Nyquist frequency. 

all-pass filter A filter that provides only phase shift or phase delay without appreciable changing the magnitude characteristic. 

ampere Abbr. I, also A. 1. A unit of electric current in the International standard meter-kilogram-second (mks) system. It is the
steady current that when flowing in straight parallel wires of infinite length and negligible cross section, separated by a distance of
one meter in free space, produces a force between the wires of 2E-7 newtons per meter of length. 2. A unit in the International
System specified as one International coulomb per second and equal to 0.999835 ampere. [After André Marie Ampère.] 

Ampère, André Marie (1775-1836) French physicist and mathematician who formulated Ampère's law, a mathematical
description of the magnetic field produced by a current-carrying conductor. 

amplitude 1. Greatness of size; magnitude. 2. Physics. The maximum absolute value of a periodically varying quantity. 3.
Mathematics. a. The maximum absolute value of a periodic curve measured along its vertical axis. b. The angle made with the
positive horizontal axis by the vector representation of a complex number. 4. Electronics. The maximum absolute value reached by
a voltage or current waveform. 

analog A real world physical quantity or data characterized by being continuously variable (rather than making discrete jumps), and
can be as precise as the available measuring technique. 

ANSI (American National Standards Institute) A private organization that develops and publishes standards for voluntary use in
the U.S.A. 

anti-aliasing filter A low-pass filter used at the input of digital audio converters to attenuate frequencies above the half-sampling
frequency to prevent aliasing. 

anti-imaging filter A low-pass filter used at the output of digital audio converters to attenuate frequencies above the half-sampling
frequency to eliminate image spectra present at multiples of the sampling frequency. 

ASA (Acoustical Society of America) Founded in 1929, the oldest organization for scientist and professional acousticians and
others engaged in acoustical design, research and education. 

ASCII (pronounced "ask-ee") (American Standard Code for Information Interchange) An ANSI standard data transmission
code consisting of seven information bits, used to code 128 letters, numbers, and special characters. Many systems now use an 8-bit
binary code, called ASCII-8, in which 256 symbols are represented (for example, IBM's "extended ASCII"). 

ASIC (application-specific integrated circuit) A large-scale integrated circuit whose function is determined by the final mask
layer for a particular application or group of applications; for example, an IC that does all the functions of a modem. 

asymmetrical (non-reciprocal) response Term used to describe the comparative shapes of the boost/cut curves for variable
equalizers. The cut curves do not mirror the boost curves, but instead are quite narrow, intended to act as notch filters. 

asynchronous A transmission process where the signal is transmitted without any fixed timing relationship between one word and
the next (and the timing relationship is recovered from the data stream). 

ATM (asynchronous transfer mode) networking An extremely fast networking technology, already found on many disk editors
(Avid Sonic Solutions, Studio Audio, etc.) and predicted to infiltrate homes within the coming decade. ATM specifies the protocol
(i.e., the order and sequence) of the digital information on the network, but not the physical means of transmission (e.g., fiber optic,
twisted-pair, etc.). The protocol controls how the entire network is run and maintained. 

atmospheric pressure Pressure caused by the weight of the atmosphere. At sea level it has a mean value of one atmosphere but
reduces with increasing altitude. 

audio 1. Of or relating to humanly audible sound, i.e., audio is all the sounds that humans hear. 2. a. Of or relating to the
broadcasting or reception of sound. b. Of or relating to high-fidelity sound reproduction. [Audio traveling through air is vibrations, or
cycles of alternating pressure zones. Rarefaction follows each cycle of compression, which produces a wave.] 

audio compression See: digital audio data compression 

auditory filter Term used to describe the concept of critical bands. Analogous to a bandpass filter with a rounded top
("rounded-exponential" after Patterson and Moore, 1986). The filter is slightly asymmetric, being wider on the low-frequency side. 

B 

bandpass filter A filter that has a finite passband, neither of the cutoff frequencies being zero or infinite. The bandpass frequencies
are normally associated with frequencies that define the half power points, i.e. the -3 dB points. 

band-limiting filters A >low-pass and a high-pass filter in series, acting together to restrict (limit) the overall bandwidth of a
system. 

bandwidth Abbr. BW The numerical difference between the upper and lower -3 dB points of a band of audio frequencies. Used to
figure the Q, or quality factor, for a filter. 

bar A unit of pressure equal to one million dynes per square centimeter. (Yeah, I know you expected some wiseacre response, but
you ain't gonna get it!) 

baud rate (pronounced "bawd"; after Baudot Code named for the French telegrapher Emile Baudot, 1845-1903) The transmitted
signaling speed, or keying rate of a modem. Often confused with bit rate. Bit rate and baud rat are NOT synonymous and shall
not be interchanged in usage. For example, one baud equals one half dot cycle per second in Morse code, one bit per second in a
train of binary signals, and one 3-bit value per second in a train of signals each of which can assume one of 8 different states, and so
on - all brought to you by the magic of advanced coding techniques that allow more than one bit per baud. Preferred usage is bit
rate, with baud used only when the details of a modem are specified. 

BCD 1. (binary-coded decimal) Pertains to a number system where each decimal digit is separately represented by a 4-bit binary
code; for example, the decimal number 23 is represented as 0010 0011 (2 = 0010 and 3 = 0011, grouped together as shown), while in
straight binary notation, 23 is represented as 10111. 2. (binary-coded digit) A digit of any number system that is represented as a
fixed number of binary digits; from the previous example, the decimal digit 23 is represented as 10111. 

bel Abbr. b, B Ten decibels. [After Alexander Graham Bell.] 

Belchfire® Series Term coined by Crown International for their mythical power amplifier, the BF-6000SUX. Based on original
research into the first principles of teramagnostriction quasar-quadrature, the BF-6000SUX could have changed the design of all
future power amps, but it didn't. In spite of Crown's leap forward into the past of technical declination, the marketplace categorically
stated that it did not want 6,000 watts per channel in only one rack space - in spite of its six-foot depth and 206 lbs weight. The only
known use of a BF-6000SUX was to drive the experimental Electro-Voice Rearaxial Softspeaker, when Rane demoed their PI 14
Pseudoacoustic Infector using Jensen's JE-EP-ERs Multi-denomial Transpedance Informer for coupling - but many consider that
only hearsay. 

Bell, Alexander Graham (1847-1922) Scottish-born American inventor of the telephone. The first demonstration of electrical
transmission of speech by his apparatus took place in 1876. Bell also invented the audiometer, an early hearing aid, and improved the
phonograph. 

bilinear transform A mathematical method used in the transformation of a continuous time (analog) function into an equivalent
discrete time (digital) function. Fundamentally important for the design of digital filters. A bilinear transform ensures that a stable
analog filter results in a stable digital filter, and it exactly preserves the frequency-domain characteristics, albeit with frequency
compression. 

binary A condition in which there are two possible states; for example, the binary number system (base-2) using the digits 0 and 1. 

bit Abbreviation for binary digit. The smallest amount of digital information. A bit can store or represent only two states, 0 and 1. 

bit clock The synchronizing signal that indicates the rate of individual data bits over a digital audio interface. 

bit error rate The number of bits processed before an erroneous bit is found (e.g., 10E13), or the frequency of erroneous bits (e.g.,
10E-13). 

bit rate The rate or frequency at which bits appear in a bit stream. The bit rate of raw data from a CD, for example, is 4.3218
MHz. 

bit stream A binary signal without regard to grouping. 

bit-mapped display A display in which each pixel's color and intensity data are stored in a separate memory location. 

BNC (bayonet Neill Concelman, or baby N-connector, or bayonet connector) A bayonet-locking connector for slim coaxial
cables. What "BNC" truly stands for is still debated: 1) There is an "N-connector," similar to, but larger than the BNC-type, used for
fat coaxial cables; 2) Neill Concelman is credited with inventing this connector; 3) And, of course, it is a bayonet-style - so, take
your pick. 

boost/cut equalizer The most common graphic equalizer. Available with 10 to 31 bands on octave to 1/3-octave spacing. The flat
(0 dB) position locates all sliders at the center of the front panel. Comprised of bandpass filters, all controls start at their center 0 dB
position and boost (amplify or make larger) signals by raising the sliders, or cut (attenuate or make smaller) the signal by lowering
the sliders on a band-by-band basis. Commonly provide a center-detent feature identifying the 0 dB position. Proponents of boosting
in permanent sound systems argue that cut-only use requires adding make-up gain which runs the same risk of reducing system
headroom as boosting. 

buffer In data transmission, a temporary storage location for information being sent or received. 

burst error A large number of data bits lost on the medium because of excessive damage to or obstruction on the medium. 

bus One or more electrical conductors used for transmitting signals or power from one or more sources to one or more destinations.
Often used to distinguish between a single computer system (connected together by a bus) and multi-computer systems connected
together by a network. 

buss To kiss. 

byte A group of eight bits (a word) operating together. 

C 

Cartesian coordinate system 1. A two-dimensional coordinate system in which the coordinates of a point in a plane are its
distances from two perpendicular lines that intersect at an origin, the distance from each line being measured along a straight line
parallel to the other. 2. A three-dimensional coordinate system in which the coordinates of a point in space are its distances from
each of three perpendicular lines that intersect at an origin. After the Latin form of Descartes, the mathematician who invented it. 

CAV (constant angular velocity) A disc rotating at a constant number of revolutions per second. The LP is a CAV system at 33
1/3 rpm. Another example is the CAV laserdisc which plays two thirty minute sides. 

CCIR (International Radio Consultative Committee) A branch of the International Telecommunications Union (ITU), a
specialized agency of the United Nations - thus the CCIR is a treaty organization related directly to the UN. The CCIR is concerned
with generating documents dealing with the preparation, transmission, and reception of all kinds of information using radio signals,
with the term "radio" being taken in the broadest sense, including television and telephony. 

CD (compact disc) Trademark term for the Sony-Philips digital audio optical disc storage system. The system stores 75 minutes
(maximum) of digital audio and subcode information, or other non-audio data, on a 12-centimeter diameter optical disc. The disc is
made of plastic, with a top metallized layer, and is read by reflected laser light. Variations (such as the 3" disc) are reserved for
special applications. 

CD-I (compact disc interactive) System storing digital audio, video, text, and graphics information interactively, with user control
over content and presentation, on a 12-centimeter diameter optical disc. 

CD+MIDI A System storing MIDI information in a disc's subcode area. 

CD-PROM (compact disc programmable read-only memory) A write-once CD-ROM disc. 

CD-R (compact disc-recordable) A compact disc that is recordable at least once. 

CD-ROM (compact disc read-only memory) A method of storing digitally coded information, such as computer information or
database, on a 12-centimeter diameter optical disc. 

CD-V (compact disc video) A system storing five minutes of analog video and digital audio plus twenty minutes of digital audio only
on a 12-centimeter diameter optical disc, and longer times on 20- or 30-centimeter diameter optical discs. 

centi- Prefix for one hundredth (10E-2), abbreviated c. 

charge Symbol q 1. Electricity. a. To cause formation of a net electric charge on or in (a conductor, for example). b. To energize
(a storage battery) by passing current through it in the direction opposite to discharge. 2. Physics. a. The intrinsic property of matter
responsible for all electric phenomena, in particular for the force of the electromagnetic interaction, occurring in two forms arbitrarily
designated negative and positive. b. A measure of this property. c. The net measure of this property possessed by a body or
contained in a bounded region of space. 

checksum The sum of a group of data items used for error checking. If the checksum received equals the one sent, all is well.
Otherwise, the receiving equipment requests the data be sent again. 

chromatic scale Music. A scale consisting of 12 semitones. 

chrominance The color portion of the video signal - includes hue and saturation information but not brightness (see luminance). 

CISC (complex instruction set computing) See: RISC 

clock A timing device that generates the basic periodic signal used as a source of synchronizing signals in digital equipment. 

CLV (constant linear velocity) A disc rotating at varying numbers of revolutions per second to maintain a constant relative velocity
between pickup and track across the disc radius. The CD is a CLV system rotating from 500 rpm (lead-in track) to 200 rpm
(lead-out track). Another example is the CLV laserdisc which plays two sixty minute sides. 

coaxial cable A single copper conductor, surrounded with a heavy layer of insulation, covered by a thick surrounding copper shield
and jacket. A constant-impedance unbalanced transmission line. 

Codec (code-decode) A device for converting voice signals from analog to digital for use in digital transmission schemes, normally
telephone based, and then converting them back again. Most codecs employ proprietary coding algorithms for data compression,
common examples being Dolby's AC-2, ADPCM, and MPEG schemes. 

combining response See: interpolating response 

compander A contraction of compressor-expander. A term referring to dynamic range reduction and expansion performed by first
a compressor acting as an encoder, and second by an expander acting as the decoder. Normally used for noise reduction or
headroom reasons. 

complex frequency variable An AC frequency in complex number form. 

complex number Mathematics. Any number of the form a + bj, where a and b are real numbers and j is an imaginary number
whose square equals -1; and a represents the real part (e.g., the resistive effect of a filter, at zero phase angle) and b represents
the imaginary part (e.g., the reactive effect, at 90 phase angle). 

composite video A video signal combining luminance, chrominance, and synchronization data on a single coax cable using RCA
connectors and color-coded yellow. 

compression 1. An increase in density and pressure in a medium, such as air, caused by the passage of a sound wave. 2. The
region in which this occurs. 

compression wave A wave propagated by means of the compression of a fluid, such as a sound wave in air. 

compressor A signal processing device used to reduce the dynamic range of the signal passing through it. For instance, an input
dynamic range of 110 dB might pass through a compressor and exit with a new dynamic range of 70 dB. This clever bit of
skullduggery is normally done through the use of a VCA (voltage controlled amplifier), whose gain is a function of a control voltage
applied to it. Thus, the control voltage is made a function of the input signal's dynamic content. [Long answer: What "compression"
is and does has evolved significantly over the years. Originally compressors were used to reduce the dynamic range of the entire
signal; with modern advances in audio technology, compressors now are used more sparingly. First the classical case: The need for
compression arose the very first time anyone tried to record or broadcast audio: the signal exceeded the medium. For example, the
sound from a live orchestra easily equals 100 dB dynamic range. Yet early recording and broadcasting medium all suffered from
limited dynamic range. Typical examples: LP record 65 dB, cassette tape 60 dB (w/noise reduction), analog tape recorder 70 dB,
FM broadcast 60 dB, AM broadcast 50 dB. Thus "6 pounds of audio into a 4 pound bag" became the necessity that mothered the
invention of the compressor (sorry). Early compressors did not have a "threshold" knob, instead, the user set a center ("hinge") point
equivalent to the midpoint of the expected dynamic range of the incoming signal. Then a ratio was set which determined the amount
of dynamic range reduction. The earlier example of reducing 110 dB to 70 dB requires a ratio setting of 1.6:1 (110/70 = 1.6). The
key to understanding compressors is to always think in terms of increasing and decreasing level changes in dB about some
set-point. A compressor makes audio increases and decreases smaller. From our example, for every input increase of 1.6 dB
above the hinge point the output only increases 1 dB, and for every input decrease of 1.6 dB below the hinge point the output only
decreases 1 dB. If the input increases by x-dB, the output increases by y-dB, and if the input decreases by x-dB, the output
decreases by y-dB, where x/y equals the ratio setting. Simple - but not intuitive and not obvious. This concept of increasing above
the set-point and decreasing below the set-point is where this oft-heard phrase comes from: "compressors make the loud sounds
quieter and the quiet sounds louder." If the sound gets louder by 1.6 dB and the output only increases by 1 dB, then the loud
sound has been made quieter; and if the sound gets quieter by 1.6 dB and the output only decreases by 1 dB, then the quiet sound
has been made louder (it didn't decrease as much). Think about it - it's an important concept. With advances in all aspects of
recording, reproduction and broadcasting of audio, the usage of compressors changed from reducing the entire program to just
reducing selective portions of the program. Thus was born the threshold control. Now sound engineers set a threshold point such
that all audio below this point is unaffected, and all audio above this point is compressed by the amount determined by the ratio
control. Therefore the modern usage for compressors is to turn down (or reduce the dynamic range of) just the loudest signals.
Other applications have evolved where compressors are used in controlling the creation of sound. For example when used in
conjunction with microphones and musical instrument pick-ups, compressors help determine the final timbre by selectively
compressing specific frequencies and waveforms. Common examples are "fattening" drum sounds, increasing guitar sustain, vocal
"smoothing," and "bringing up" specific sounds out of the mix, etc.] 

constant-Q equalizer (also constant-bandwidth) Term applied to graphic and rotary equalizers describing bandwidth behavior as
a function of boost/cut levels. Since Q and bandwidth are inverse sides of the same coin, the terms are fully interchangeable. The
bandwidth remains constant for all boost/cut levels. For constant-Q designs, the skirts vary directly proportional to boost/cut
amounts. Small boost/cut levels produce narrow skirts and large boost/cut levels produce wide skirts. 

convolution A mathematical operation producing a function from a certain kind of summation or integral of two other functions. In
the time domain, one function may be the input signal, and the other the impulse response. The convolution than yields the result of
applying that input to a system with the given impulse response. In DSP, the convolution of a signal with FIR filter coefficients
results in the filtering of that signal. 

correlation A mathematical operation that indicates the degree to which two signals are alike. 

crest factor The term used to represent the ratio of the peak (crest) value to the RMS value of a waveform. 

critical band Physiology of Hearing. A range of frequencies that is integrated (summed together) by the neural system, equivalent
to a bandpass filter (auditory filter) with approximately 10-20% bandwidth (approximately one-third octave wide). [Although the
latest research says critical bands are more like 1/6-octave above 500 Hz, and about 100 Hz wide below 500 Hz.] The ear can be
said to be a series of overlapping critical bands, each responding to a narrow range of frequencies. Introduced by Fletcher (1940) to
deal with the masking of a pure-tone by wideband noise. 

current Symbol i, I Electricity. a. A flow of electric charge. b. The amount of electric charge flowing past a specified circuit point
per unit time, or the rate of flow of electrons. [As electrons flow in one direction, the spaces left behind, called holes, appear to flow
in the opposite direction. Thus, current can be visualized as electron flow (negative current flow), or in the opposite direction, hole
flow (positive current flow, sometimes called conventional current flow).] 

current loop A data transmission scheme that looks for current flow rather than voltage levels. This systems recognizes no current
flow as a binary zero, and having current flow as a binary one. Favored for its low sensitivity to cable impedance. MIDI is an
example of a current loop interconnect system. 

cut-only equalizer Term used to describe graphic equalizers designed only for attenuation. (Also referred to as notch equalizers, or
band-reject equalizers). The flat (0 dB) position locates all sliders at the top of the front panel. Comprised only of notch filters
(normally spaced at 1/3-octave intervals), all controls start at 0 dB and reduce the signal on a band-by-band basis. Proponents of
cut-only philosophy argue that boosting runs the risk of reducing system headroom. 

cutoff frequency Filters. The frequency at which the signal falls off by 3 dB (the half power point) from its maximum value. Also
referred to as the -3 dB points, or the corner frequencies. 

D 

DA-88 Tascam's model number for their digital multitrack recorder using Sony-developed "Hi8" 8 mm video tape as the storage
medium. Becoming a generic term describing this family of recorders. See: DTRS 

DAB (digital audio broadcast) NRSC (National Radio Systems Committee) term for the next generation of digital radio broadcast.

DAC (or D/A, digital-to-analog converter) The electronic component which converts digital words into analog signals that can
then be amplified and used to drive loudspeakers, etc. The DAC is the last link in the digital chain of signal processing 

DAR (digital audio radio) EIA