Page 158 - Electrical Engineering Dictionary

compression ratio the ratio of the num- ated processing units, memory, and periph-
ber of bits used to represent a signal before eral equipment for input and output. Uses
compression to that used after compression. internal memory for storing programs and/or
data.
Compton laser free-electron laser in
which the amplification mechanism is con- computer architecture an image of a
sidered to be Compton scattering. computing system as seen by a most sophis-
ticated computer user and programmer. The
compulsator the compulsator (compen- above concept of a programmer refers to a
sated pulsed alternator or CPA), is a specially person capable of programming in machine
designed rotating electrical alternator with language, including the capability of writing
a very low internal impedance that allows a compiler. The architecture includes all reg-
it to produce large, repetitive pulses of cur- istersaccessiblebyanyinstruction(including
rent. These machines produce an alternating the privileged instructions), the complete in-
current output whose frequency is dependent struction set, all instruction and data formats,
upon the rotor speed and number of magnetic addressing modes, and other details that are
poles in the CPA. Typical output voltages of necessary in order to write any program. This
a CPA are 1,000–10,000 volts with output definition stems from the IBM program of
currents of up to 5,000,000 amperes and fre- generating the 360 system in the early 1960s.
quencies of 100–1,000 hertz. Contrast with computer organization. See
also Flynn’s taxonomy.
compulsory miss See cold start miss.
computer communication network col-
computational cut-off rate See cut-off
lection of applications hosted on different
rate.
machines and interconnected by an infras-
tructure that provides intercommunications.
computational electromagnetics the use
of modern digital hardware to obtain solu-
computer generated hologram a holo-
tions to Maxwell’s equations and to visualize
gram where the required complex amplitude
these solutions.
and phase functions are generated by com-
computational intelligence See soft puter and written onto an optical medium.
computing.
computer hardware description language
computed tomography (CT) See tomog- (CHDL) examples include VHDL and
raphy. Verilog, current work in CHDL includes
mainly languages for verification, and exten-
computer (1) an electronic, electrome- sions of existing languages for system de-
chanical, or purely mechanical device that scription and analog design. CHDL confer-
accepts input, performs some computational ences are organized every year.
operations on the input, and produces some
output. computer model a computer model of
(2) functional unit that can perform sub- a device consists of a mathematical/logical
stantial computations, including numerous model of the behavior of the device repre-
arithmetic operations, or logic operations, sented in the form of a computer program.
without human intervention during a run. A good computer model reproduces all the
(3) general or special-purpose program- behaviors of the physical device in question
mable system that is able to execute programs and can be confidently used to simulate the
automatically. It has one or more associ- device in a variety of circumstances.

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2000 by CRC Press LLC