18WuD2x

172 decimal-coded digit • decommutation
decimal-coded digit 1. A numeral from 0 to 9. 2.
A numeral in the DECIMAL NUMBER SYSTEM.
3. A binary representation of a decimal value
from 0 to 9.
decimal digit A numeral from 0 to 9.
decimal equivalent The decimal number equal to
a given fraction (e.g., the decimal equivalent of
21
⁄64 is 0.3281).
decimal fraction See DECIMAL, 2.
decimal notation See DECIMAL NUMBER SYS-
TEM.
decimal number system The familiar base-10 or
radix-10 number system, in which the digits 0
through 9 represent values according to their position,
relative to the decimal point (also called
the radix point). Positions to the left of the point
represent successive positive powers of 10, and
those to the right represent successive negative
powers of 10.
decimal point The radix point in a decimal number.
It serves to separate the integral part from
the fractional part of the number.
decimeter waves See MICROWAVES.
decimetric waves Electromagnetic waves having
lengths ranging from 0.1 meter to 1 meter (3000
MHz to 300 MHz). Also known as ultrahigh frequency
(UHF).
decineper A natural-logarithmic unit equal to 0.1
neper.
decipher See DECODING, 3.
decision 1. A choice based on the evaluation and
comparison of data, and the identification of a
specified objective. 2. In digital computer operations,
the automatic selection of the next step in
a sequence, on the basis of data being compared
by a relational test.
decision box A block on a computer flowchart indicating
the point at which a decision (see DECI-
SION, 2) must be made as to which of several
branches the program will take.
decision elements See LOGIC CIRCUITS.
decision instruction A computer program
instruction to compare the values of operands
and take an appropriate action, as per the BASIC
instruction “IF A = B THEN GO TO (line number).”
decision procedure In decision theory, a series of
calculations made to optimize the speed or efficiency
of a process, or to minimize risk, failure,
cost, etc.
decision theory A statistical discipline concerned
with identifying and evaluating choices and alternatives,
and determining the best sequence of
steps to take in reaching an objective.
decision tree In decision theory, a diagram showing
alternative choices, so called from its resemblance
to a tree with branches.
decision value A value that defines the boundary
between two intervals in the encoding process.
deck 1. See TAPE DECK. 2. A pack of punched
cards in a computer file.
declarative macroinstruction As part of an assembly
language, instructions to the compiler to
do something or record a condition without affecting
the object program.
declarative statement A computer source program
instruction specifying the size, format, and
kind of data elements and variables in a program
for a compiler.
declination 1. The angle representing the deviation
of magnetic north from true north; it is the
angle subtended by a freely turning magnetic
needle and the meridian. Compare INCLINATION.
2. Celestial latitude.
Magnetic
north
True
north θ = Declination
θ
Compass needle
declination, 1
declinometer An instrument for measuring declination.
decode 1. To unscramble a coded message. 2. In
digital computer operations, to deliver a specific
output from character-coded inputs. 3. In a multiplex
system, the separation of the subcarrier
from the main carrier.
decoder A circuit or device for performing DECOD-
ING.
decoder/demultiplexer A circuit that places an
input signal on a selected output line.
decoder/driver An integrated circuit containing a
decoder and driver.
decoding 1. In computer and data-processing operations,
DIGITAL-TO-ANALOG CONVERSION.
2. The conversion to English of a message received
in a code. 3. Translating a message from a
secret code (i.e., deciphering a message). 4. The
automatic conversion of a signal into the appropriate
switching action (as the enabling of a
transmitter or receiver by a tone in a selective
calling system).
decoding circuit A circuit intended for the purpose
of translating a code into ordinary language.
decollator An offline computer device for separating
the parts of output continuous stationery
sets. Also see CONTINUOUS STATIONERY.
decommutation The extraction of a signal component
from the composite signal, resulting from
commutation.