18WuD2x

434 mask • master program file
mask 1. A kind of stencil through which plating,
electrodeposition, or diffusion can be done.
2. The viewing screen, or GRATICULE, of an oscilloscope.
3. To obliterate a signal with a stronger
one. 4. A bit or character pattern used to change
or extract bit positions in another pattern.
masking 1. The use of a MASK of any type. 2. The
tendency of one effect or phenomenon to obscure
another. It applies especially in audio systems,
where certain sounds impair the ability of a listener
to hear other sounds that occur at the same
time. 3. The extent to which one effect or phenomenon
obscures another.
Masonite Masonite Corporation’s tough fiberboard
used for panels and bases of some electronic
equipment.
mass The quantity of matter in a body. Like weight,
mass is expressed in kilograms in the metric (SI)
system and in pounds in the English system. For
a given piece of material, mass can be determined
by dividing the weight by the acceleration of gravity.
mass data Data in excess of the maximum amount
that can be stored in the main (internal) storage
unit of a digital computer (i.e., that which can
only be accommodated by external media such as
magnetic disks or tapes).
mass-energy equation Energy (E) is the product of
a given mass (m) and the square of the speed of
light (c 2 ): E = mc 2 . It is also called the Einstein
equation.
mass number 1. Symbol, A. A number representing
the total of neutrons and protons in the nucleus
of an atom. The approximate mass of an
atom is equal to A × m p , where m p is the total proton
(rest) mass. 2. The number indicating the
sum of nuclear protons and neutrons in an atom.
It is usually written following the symbol for the
atom: thus, U238 is uranium having 238 nucleons.
An isotope of an element will have a different
mass number than that of the normal atom.
mass of electron at rest Symbol, m e . The amount
of matter in an electron; m e = 9.1093897 ×
10 –31 kg.
mass of neutron at rest Symbol, m n . The mass of
a neutron in the nucleus of an atom; m n =
1.6749286 × 10 –27 kg.
mass of proton at rest Symbol, m p . The mass
of a proton in the nucleus of an atom; m p =
1.6726231 × 10 –27 kg.
mass resistivity 1. The resistance of a wire one
meter long having a mass of one gram. It varies,
depending on the composition of the wire. 2. The
resistance of a wire one mile long having a weight
of one pound. It varies, depending on the composition
of the wire.
mass spectograph An instrument used to analyze
chemical compounds and mixtures in
terms of their distinctive mass spectra, exhibited
by ionized samples of the materials in a
magnetic field.
mass spectrometer Abbreviation, MS. An instrument
that permits rapid analysis of chemical
compounds via the MASS SPECTRUM.
mass spectrum An electron spectrum that can be
used to identify a chemical element. Different elements
have nuclei with different charge-to-mass
ratios. This results in each element having a
unique mass spectrum.
mass storage In a computer system, a magnetic or
optical storage medium capable of holding large
amounts of data. Examples: magnetic diskette,
magneto-optical diskette, external hard disk,
compact-disk read-only memory (CD-ROM), and
magnetic tape.
mass unit See ATOMIC MASS UNIT.
master 1. The primary or main element or device
in a system. 2. A primary data medium or recording
from which copies are made. 3. A primary
reference standard. See the following several
definitions.
master clock 1. In a digital computer, the primary
generator of timing pulses. 2. A standard time
clock that drives other (slave) clocks, or to which
clocks of lesser accuracy can be referred.
master console In a computer system, an equipment
with panel instruments and controls, which
permits operations to be governed, monitored,
and controlled by a human operator.
master control 1. The main control circuit in a
system. 2. A point from which signals or programs
are distributed in a communications or
broadcast system.
master data Also called archives. In a computer
record, data elements that remain unaltered for a
long time, and from which copies are made.
master file A computer file of data used routinely
and remaining unchanged for a long time.
master gain control The principal gain control in
an audio amplifier or mixer [i.e., the one used to
adjust the gain (volume) of the entire system].
master instruction tape Magnetic tape on which
various related computer programs are recorded.
master library tape See MASTER PROGRAM FILE.
master oscillator Abbreviation, MO. The main oscillator
in an electronic system (e.g., the oscillator
stage in an oscillator-amplifier type of radio
transmitter). This oscillator can be either selfexcited
or crystal-controlled.
master oscillator-power amplifier Abbreviation,
MOPA. A type of transmitter or signal generator
in which a frequency-determining oscillator
drives a power amplifier, which in turn delivers
an output signal. Because the oscillator is isolated
from the output load, this arrangement has
greater stability than one in which the oscillator
alone supplies power to the load.
master pattern The etching pattern used for manufacture
of a batch of identical printed-circuit
boards.
master program file A reel of magnetic tape on
which is recorded the programs regularly used in