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filament • filler 283
filament In a vacuum tube or incandescent lamp,
the thin wire heated by electric current; it emits
electrons, light, and heat. The filament is the
cathode in a filament-type tube, but serves only
to heat indirectly the cathode sleeve in an indirectly
heated tube.
filament battery See A BATTERY.
filament choke A radio-frequency (RF) choke operated
in the filament lead of an electron tube.
Such chokes are necessary in filament-type tubes
in RF power amplifiers.
filament circuit The circuit carrying filament current.
filament coil See FILAMENT WINDING.
filament current Symbol, I F . The current flowing
through the filament of a vacuum tube.
filament emission Electrons emitted directly by
the filament in an electron tube (thermionic emission)
or the amount of such emission.
filament hum A hum signal caused by voltage induced
in a circuit by the alternating-current (ac)-
operated filaments (heaters) of tubes or by the
filament wiring.
filament lag The time delay in the heating and
cooling of an ac tube or lamp filament as filament-current
changes polarity.
filament power supply A source of power, usually
alternating-current, for heating the filament of a
vacuum tube or tubes.
filament resistance 1. The resistance of the filament
in an electron tube or incandescent
lamp. 2. The resistance of an external dropping
resistor in the filament circuit of a tube or
lamp.
filament transformer A step-down transformer
that supplies power exclusively to the filament
(heater) of an electron tube.
filament-type bolometer A BOLOMETER in
which the sensitive element is a wire filament.
Examples: barretter, incandescent lamp, and
wire fuse.
filament voltage Symbol, V F . The voltage across
the filament of an electron tube.
filament winding In a power transformer, the coil
that supplies heating power to the filament of a
vacuum tube. Also called FILAMENT COIL.
file An organized collection of records related by a
common format, data source, or application.
file conversion Converting data files from one
form to another, often for the purpose of making
them compatible with other computers.
file gap An area of a data medium that signifies the
end of a file; it can also mark the start of another
file.
file identification A code that identifies a file.
file label File identification in which the first
record in the file is a set of characters unique to
the file; it conveys such information about (for example,
a tape file as a description of content, generation
number, reel number, date of writing,
etc.). Also called HEADER LABEL.
file layout How the contents of a file are organized;
usually defined by the system or specified by a
program.
file maintenance To delete, add, or correct records
in a file. Unlike updating, which is done to reflect
changes in events recorded in the file, maintenance
ensures that the contents of the file are accurate
records of the necessary data.
file management A method of storing and recalling
data from computer storage media, such as
magnetic disks.
filename In a computer file label, the alphanumeric
character set that identifies and describes
the file. It generally consists of one to eight characters,
often including an extension of one to
three characters. In some computer operating
systems, filenames can be much longer (e.g., up
to 32 characters). See FILENAME EXTENSION.
filename extension A group of one, two, or three
characters following the main body of a FILE-
NAME, and separated from it by a period (.). It
generally denotes the application or purpose of
the file. The extension .BAK, for example, denotes
a backup file; .TXT denotes a text file; .BMP denotes
a bit-mapped graphics file.
file organization The way words, bits, or records
are physically arranged in the storage medium for
a file, possibly including the method of access (serial,
alphabetical, random, etc.).
file-oriented programming Computer programming
that uses a general file and record-control
program to simplify I/O coding.
file-oriented system A system having file storage
as its basis.
file print A hard copy (printout) of the contents of
a file.
file processing The operations associated with
making and using files.
file protection Preventing the possibility of writing
over data files before they are made available for
use. It is usually done by having a program check
file labels.
file reconstitution Restoring a partially or completely
damaged file by updating a previous generation
of the file using a file of interim transactions.
file recovery Following the interruption of file processing
because of system failure, the procedure
for reestablishing the file’s condition as necessary
for the resumption of processing without losing
accuracy.
file section Part of a file in certain consecutive locations
on a storage medium.
file security Protective and security measures
(e.g., the issuance of clearances, status markers,
etc.) as they relate to computer files.
file set A collection of interrelated files stored consecutively
in a magnetic disk volume (package).
fill The percentage of lines in a cable that are actually
in use at a given time.
filler A nonessential data part used, for example,
to bring a record to a standard size.