C
n.
A programming language developed by Dennis Ritchie at Bell
Laboratories in 1972. It is so named because its immediate
predecessor was the B programming language. Although C is
considered by many to be more a machine-independent assembly
language than a high-level language, its close association
with the UNIX operating system, its enormous popularity, and
its standardization by the American National Standards
Institute (ANSI) have made it perhaps the closest thing to a
standard programming language in the
microcomputer/workstation marketplace. C is a compiled
language that contains a small set of built-in functions
that are machine dependent. The rest of the C functions are
machine independent and are contained in libraries that can
be accessed from C programs. C programs are composed of one
or more functions defined by the programmer; thus C is a
structured programming language. See also C++,
compiled language, library, Objective-C, structured
programming.
C++
n.
An object-oriented version of the C programming language,
developed by Bjarne Stroustrup in the early 1980s at Bell
Laboratories and adopted by a number of vendors, including
Apple Computer and Sun Microsystems. See also C,
Objective-C, object-oriented programming.
C2
n.
The lowest level of security in the U.S. National Computer
Security Center's hierarchy of criteria for trusted computer
systems, requiring user logon with password and a mechanism
for auditing. The C2 level is outlined in the Orange Book.
See also Orange Book (definition 1).
cabinet
n.
The box in which the main components of a computer (CPU, the
hard drive, floppy and CD-ROM drives, and expansion slots
for peripheral devices, such as monitors) are located.
See also CPU, expansion slot.
cable
n.
A collection of wires shielded within a protective tube,
used to connect peripheral devices to a computer. A mouse, a
keyboard, and a printer might all be connected to a computer
with cables. Printer cables typically implement a serial or
a parallel path for data to travel along.
cable connector
n.
The connector on either end of a cable. See also DB
connector, DIN connector, RS-232-C standard, RS-422/423/449.
cable modem
n.
A modem that sends and receives data through a coaxial cable
television network instead of telephone lines, as with a
conventional modem. Cable modems, which have speeds of 500
kilobits per second (Kbps), can generally transmit data
faster than current conventional modems. See also
coaxial cable, modem.
cabling diagram
n.
A plan that shows the path of cables that attach computer
system components or peripherals. Cabling diagrams are
particularly important for explaining the connection of disk
drives to a disk controller.
cache
n.
A special memory subsystem in which frequently used data
values are duplicated for quick access. A memory cache
stores the contents of frequently accessed RAM locations and
the addresses where these data items are stored. When the
processor references an address in memory, the cache checks
to see whether it holds that address. If it does hold the
address, the data is returned to the processor; if it does
not, a regular memory access occurs. A cache is useful when
RAM accesses are slow compared with the microprocessor
speed, because cache memory is always faster than main RAM
memory. See also disk cache, wait state.
CAD
n.
Acronym for computer-aided design. A system of programs and
workstations used in designing engineering, architectural,
and scientific models ranging from simple tools to
buildings, aircraft, integrated circuits, and molecules.
Various CAD applications create objects in two or three
dimensions, presenting the results as wire-frame
"skeletons," as more substantial models with shaded
surfaces, or as solid objects. Some programs can also rotate
or resize models, show interior views, generate lists of
materials required for construction, and perform other
allied functions. CAD programs rely on mathematics, often
requiring the computing power of a high-performance
workstation. See also CAD/CAM, I-CASE.
caddy
n.
A plastic carrier that holds a CD-ROM and is inserted into a
CD-ROM drive. Some personal computers, especially older
models, have CD-ROM drives that require the use of a caddy.
Most current CD-ROM drives do not require a caddy.
calculator
n.
Broadly, any device that performs arithmetic operations on
numbers. Sophisticated calculators can be programmed for
certain functions and can store values in memory, but they
differ from computers in several ways: they have a fixed set
of commands, they do not recognize text, they cannot
retrieve values stored in a data file, and they cannot find
and use values generated by a program such as a spreadsheet.
calendar program
n.
An application program in the form of an electronic
calendar, commonly used for highlighting dates and
scheduling appointments. Some calendar programs resemble
wall calendars, displaying dates in blocks labeled with the
days of the week; others display dates day by day and enable
the user to enter appointments, notes, and other memoranda.
A day-of-the-week type of calendar program could, for
example, be used to find out that Christmas 1999 will be on
a Saturday. Depending on its capabilities, such a program
might cover only the current century, or it might cover
hundreds of years and even allow for the change (in 1582)
from the Julian to the Gregorian calendar. A
calendar/scheduler program might show blocks of dates or,
like an appointment book, single days divided into hours or
half hours, with room for notes. Some programs allow the
user to set an alarm to go off at an important point in the
schedule. Other programs can coordinate the calendars of
different people on the same network, so that a person
entering an appointment into his or her calendar also enters
the appointment into a colleague's calendar.
call1
n.
In a program, an instruction or statement that transfers
program execution to some section of code, such as a
subroutine, to perform a specific task. Once the task is
performed, program execution resumes at the calling point in
the program. See also calling sequence.
call2
vb.
1. To establish a connection through a telecommunications
network. 2. To transfer program execution to some section of
code (usually a subroutine) while saving the necessary
information to allow execution to resume at the calling
point when the called section has completed execution. Some
languages (such as FORTRAN) have an explicit CALL statement;
others (such as C and Pascal) perform a call when the name
of a procedure or function appears. In assembly language,
there are various names for a CALL instruction. When a
subroutine call occurs in any language, one or more values
(known as arguments or parameters) are often passed to the
subroutine, which can then use and sometimes modify these
values. See also argument, parameter.
callback
n.
A user authentication scheme used by computers running
dial-in services. A user dials in to a computer and types a
logon ID and password. The computer breaks the connection
and automatically calls the user back at a preauthorized
number. This security measure helps prevent unauthorized
access to an account even if an individual's logon ID and
password have been stolen. See also authentication.
camera-ready
adj.
In publishing, of or pertaining to the stage at which a
document, with all typographic elements and graphics in
place, is suitably prepared to be sent to a printing
service. The printing service photographs the camera-ready
copy and then uses the photograph to make plates for
printing. Some applications are advertised as being able to
bring documents to the camera-ready stage, eliminating the
need for manual layout and pasteup of elements onto boards.
cancel
n.
A control character used in communication with printers and
other computers, commonly designated as CAN. It usually
means that the line of text being sent should be canceled.
In ASCII, which is the basis of character sets used by most
microcomputers, this is represented internally as character
code 24.
canned software
n.
Off-the-shelf software, such as word processors and
spreadsheet programs.
capacitor
n.
A circuit component that provides a known amount of
capacitance (ability to store an electric charge). A
capacitor typically consists of two conductive plates
separated by an insulating (dielectric) material. If other
factors remain constant, capacitance increases as the plates
are made larger or brought closer together. A capacitor
blocks direct current but passes alternating current to an
extent that depends on its capacitance and on the frequency
of the current. See also capacitance.
capacity
n.
The amount of information a computer or an attached device
can process or store. See also computer.
caps
n.
Short for capital letters. Compare lowercase.
Caps Lock key
n.
A toggle key that, when on, shifts the alphabetic characters
on the keyboard to uppercase. The Caps Lock key does not
affect numbers, punctuation marks, or other symbols.
capture
vb.
In communications, to transfer received data into a file for
archiving or later analysis.
card
n.
1. A printed circuit board or adapter that can be plugged
into a computer to provide added functionality or new
capability. These cards provide specialized services, such
as mouse support and modem capabilities, that are not built
into the computer. See also adapter, board, printed
circuit board. 2. In programs such as the HyperCard
hypertext program, an on-screen representation of an index
card on which information can be stored and "filed" (saved)
for future reference. See also hypertext. 3. A manila
card about 3 inches high by 7 inches long on which 80
columns of data could be entered in the form of holes
punched with a keypunch machine. The punched holes
corresponded to numbers, letters, and other characters and
could be read by a computer that used a punched-card reader.
Also called punched card. See also card reader
(definition 2).
card reader
n.
1. An input device used chiefly for identification purposes
that reads information that has been magnetically encoded,
usually in two tracks, on a plastic card, such as a credit
card or an employee badge. 2. A mechanical apparatus that
reads computer data from punched cards. No longer in
widespread use, card readers allow computer data to be
created offline and then input to the computer for
processing. This need for offline data creation was because
of limited CPU resources. Reading batches of punched cards
was a better use of CPU time than waiting for a human
operator to key data directly into the computer's memory.
Also called punched-card reader.
caret
n.
The small, upward-pointing symbol (^) typically found over
the 6 key on the top row of a microcomputer keyboard. In
some programming languages, the caret is used as an
exponentiation operator. For example, the expression 3 ^ 2
represents the number 3 raised to the second power. The
caret is also used to represent the Control key on the
keyboard. For example, ^Z means "hold the Control key down
and press the Z key."
carpal tunnel syndrome
n.
A form of repetitive strain injury to the wrist and hand.
Making the same small motions over and over can cause
swelling and scarring of the soft tissue of the wrist, which
then compresses the main nerve leading to the hand. Symptoms
of carpal tunnel syndrome include pain and tingling in the
fingers, and in advanced cases, carpal tunnel syndrome can
lead to loss of functionality of the hands. Typing at a
computer keyboard without proper wrist support is a common
cause of carpal tunnel syndrome. See also repetitive
strain injury, wrist support. Acronym: CTS.
carriage return
n.
A control character that tells a computer or printer to
return to the beginning of the current line. A carriage
return is similar to the return on a typewriter but does not
automatically advance to the beginning of a new line. For
example, a carriage-return character alone, received at the
end of the words
This is
a sample line of text
would cause the cursor or printer to return to the first
letter of the word This. In the ASCII character set,
the carriage-return character has the decimal value of 13
(hexadecimal 0D).
carrier
n.
1. In communications, a specified frequency that can be
modulated to convey information. 2. A company that provides
telephone and other communications services to consumers.
carrier frequency
n.
A radio-frequency signal, such as those used with modems and
on networks, used to transmit information. A carrier
frequency is a signal that vibrates at a fixed number of
cycles per second, or hertz (Hz), and is modulated (changed)
in either frequency or amplitude to enable it to carry
intelligible information.
carrier system
n.
A communications method that uses different carrier
frequencies to transfer information along multiple channels
of a single path. Transmission involves modulating the
signal on each frequency at the originating station and
demodulating the signal at the receiving station.
cartridge
n.
Any of various container devices that usually consist of
some form of plastic housing. See also disk
cartridge, ink cartridge, memory cartridge, ribbon
cartridge, ROM cartridge, tape cartridge, toner cartridge.
cartridge font
n.
A font contained in a plug-in cartridge and used to add
fonts to laser, ink-jet, or high-end dot-matrix printers.
Cartridge fonts are distinguished both from internal fonts,
which are contained in ROM in the printer and are always
available, and from downloadable (soft) fonts, which reside
on disk and which can be sent to the printer as needed.
See also font cartridge. Compare internal font.
cascade
n.
1. Additional elements displayed by a menu item or list box
from which the user can choose in order to interact with
other screen elements. 2. In newsgroup articles, the
accumulation of quotation marks (often angle brackets) added
by newsgroup readers each time an article is replied to.
Most newsgroup readers will copy the original article in the
body of the reply; after several replies, the original
material will have several quotation marks. See also
article, newsgroup, newsreader.
cascading menu
n.
A hierarchical graphical menu system in which a side menu of
subcategories is displayed when the pointer is placed on the
main category.
cascading style sheets
n.
A Hypertext Markup Language (HTML) specification developed
by The World Wide Web Consortium (W3C) that allows authors
of HTML documents and users to attach style sheets to HTML
documents. The style sheets include typographical
information on how the page should appear, such as the font
of the text in the page. This specification also directs the
way in which the style sheets of the HTML document and the
user's style will blend. Cascading style sheets have been
proposed for the HTML 3.2 standard. Also called
Cascading Style Sheet mechanism, CSS1. See also HTML,
style sheet.
cascading windows
n.
A sequence of successive, overlapping windows in a graphical
user interface, displayed so that the title bar of each is
visible. Also called overlaid windows.
case
n.
In text processing, an indication of whether one or more
alphabetic characters are capitalized (uppercase) or not
(lowercase). A case-sensitive program or routine
distinguishes between uppercase and lowercase letters and
treats the word cat as totally distinct from either
Cat or CAT. A case-sensitive program that also
separates capitalized and lowercased words would list
Arkansas
before aardvark or antimony, even though its
alphabetic position follows both lowercased words.
CASE
n.
Acronym for computer-aided software engineering. A
comprehensive label for software designed to use computers
in all phases of computer program development, from planning
and modeling through coding and documentation. CASE
represents a working environment consisting of programs and
other development tools that help managers, systems
analysts, programmers, and others to automate the design and
implementation of programs and procedures for business,
engineering, and scientific computer systems.
case-sensitive search
n.
A search in a database in which capitalization of key words
must exactly match the capitalization of words in the
database. A case-sensitive search for "north and south"
would fail to find a database entry for "North and South."
cassette
n.
The unit consisting of both the plastic case and the
magnetic tape it contains. Cassette tapes are used for
backing up large amounts of computer data.
cassette tape
n.
1. The tape within a cassette. 2. The unit consisting of
both the plastic cassette case and the tape it contains.
CAT
n.
1. Acronym for computer-aided testing. A procedure used by
engineers for checking or analyzing designs, especially
those created with CAD programs. Computer-aided testing is
also used by software developers for automated regression
testing. 2. Acronym for computer-assisted teaching. 3.
Acronym for computerized axial tomography. A medical
procedure in which a computer is used to generate a
three-dimensional image of a body part from a series of X
rays taken as cross sections along a single axis. See
CAI.
catalog
n.
1. In a computer, a list containing specific information,
such as name, length, type, and location of files or of
storage space. 2. In a database, the data dictionary. See
also data dictionary.
CBT
n.
Acronym for computer-based training. The use of computers
and specially developed tutorial programs for teaching. CBT
uses color, graphics, and other attention-getting aids to
help maintain interest, and it has both simple and
sophisticated applications. A software developer, for
example, might include a series of CBT lessons with an
application to give new users a hands-on feel for the
program; a consultant might use a longer and more detailed
CBT program as a tool in a management-training seminar.
cc
n.
Acronym for courtesy copy. A directive to an e-mail program
to send a complete copy of a given piece of mail to another
individual. The use of cc mail addressing, as opposed to
directly addressing the mail to a person, generally implies
that the recipient is not required to take any action; the
message is for informational purposes only. In a cc
directive, the fact that this recipient received the mail is
printed in the mail header and is thus known to all other
recipients. Also called carbon copy. See also
e-mail, header. Compare bcc.
CCITT
n.
Acronym for Comité Consultatif International Télégraphique
et Téléphonique. Also known as the International Telegraph
and Telephone Consultative Committee. An organization based
in Geneva, Switzerland, and established as part of the
United Nations International Telecommunications Union (ITU).
Its functions have been taken over by the ITU. The ITU
recommends use of communications standards that are
recognized throughout the world. Protocols established by
the ITU are applied to modems, networks, and facsimile
transmission. See also CCITT Groups 1-4, CCITT V
series, CCITT X series.
CCITT Groups 1-4
n.
A set of four standards recommended by the Comité
Consultatif International Télégraphique et Téléphonique
(International Telegraph and Telephone Consultative
Committee) for the encoding and transmission of images over
fax machines. Groups 1 and 2 relate to analog devices and
are generally out of use. Groups 3 and 4, which deal with
digital devices, are outlined below. Group 3 is a widespread
standard that supports standard images of 203 horizontal
dots per inch (dpi) by 98 vertical dpi and fine images of
203 horizontal dpi by 198 vertical dpi; supports two methods
of data compression, one (based on the Huffman code)
reducing an image to 10 to 20 percent of the original, the
second (READ, for relative element address designate)
compressing images to 6 to 12 percent of the original; and
provides for password protection and for polling so that a
receiving machine can request transmission as appropriate.
Group 4, a newer standard, supports images of up to 400 dpi;
data compression based on a beginning row of white pixels
(dots), with each succeeding line encoded as a series of
changes from the line before, compressing images to 3 to 10
percent of the original; does not include error-correction
information in the transmission; and requires an Integrated
Services Digital Network (ISDN) phone line rather than a
dial-up line.
CCITT V series
n.
A set of recommendations developed by the Comité Consultatif
International Télégraphique et Téléphonique (International
Telegraph and Telephone Consultative Committee) for
standardizing modem design and operations. The complete
series includes a number of recommendations covering
signaling, coding, and circuit characteristics, as well as
modems. Those most relevant to computer users are briefly
described below in terms of the modems they standardize:
k:\compdict\database\3764.doc
CCITT X series
n.
A set of recommendations adopted by the International
Telecommunications Union (ITU-T), formerly the CCITT, and
ISO for standardizing equipment and protocols used in both
public-access and private computer networks. Some of the
recommendations in the X series include the following:
k:\compdict\database\2468.doc
cd
n.
Acronym for change directory. In MS-DOS, UNIX, and FTP
client programs, the command that changes the current
directory to the directory whose path follows cd in
the command. See also directory, path.
CD
1. Acronym for Carrier Detect, a
signal sent from a modem to the attached computer to
indicate that the modem is on line. See also DCD. 2.
Acronym for compact disc. See also CD-I, CD-ROM,
compact disc.
CDF
n.
Short for Channel Definition Format.
CDFS
n.
1. Acronym for CD-ROM File System. A 32-bit protected-mode
file system that controls access to the contents of CD-ROM
drives in Windows 95. See also protected mode. 2. A
designation used with UNIX computers to indicate that a file
system resides on a read-only removable medium (that is a
CD-ROM). This usually implies that the compact disc is
compliant with the ISO 9660 standard. CDFS is also used as a
part of commands that mount media (hard drives, tape drives,
remote networked drives, and CD-ROMs) for use on a computer.
See also CD-ROM, ISO 9660.
CD Plus
n.
A compact disc encoding format that allows mixing of audio
recordings and computer data on the same CD, without the
possibility of audio equipment becoming damaged by
attempting to play the data sections.
CD recorder
n.
A device used to write CD-ROMs. Because a disc can be
written only once on these machines, they are used most
commonly to create CD-ROMs for data archival or to produce
CD-ROM masters that can be duplicated for mass distribution.
Also called CD-R machine, CD-ROM burner. See also
CD-ROM.
CD-ROM
n.
1. Acronym for compact disc read-only memory. A form of
storage characterized by high capacity (roughly 650
megabytes) and the use of laser optics rather than magnetic
means for reading data. Although CD-ROM drives are strictly
read-only, they are similar to CD-R drives (write once, read
many), optical WORM devices, and optical read-write drives.
See also CD-I, CD-R, WORM. 2. An individual compact
disc designed for use with a computer and capable of storing
up to 650 megabytes of data. See also compact disc,
disc.
CD-ROM drive
n.
A disk storage device that uses compact disc technology.
See also CD-ROM, compact disc.
CD-ROM jukebox
n.
A CD-ROM player that can contain up to 200 CD-ROMs and is
connected to a CD-ROM drive in a personal computer or
workstation. A user can request data from any of the CD-ROMs
in the jukebox, and the device will locate and play the disk
that contains the data. While only one CD-ROM can be played
at a time, if multiple CD-ROM jukeboxes are each connected
to separate CD-ROM drives that are daisy-chained together to
the computer, more than one CD-ROM can be used at a time.
See also CD-ROM, CD-ROM drive, daisy chain.
CDV
n.
1. Acronym for compressed digital video. The compression of
video images for high-speed transmission. 2. Acronym for
compact disc video. A 5-inch videodisc. See also
videodisc.
cell
n.
1. The intersection of a row and a column in a spreadsheet.
Each row and column in a spreadsheet is unique, so each cell
can be uniquely identified--for example, cell B17, at the
intersection of column B and row 17. Each cell is displayed
as a rectangular space that can hold text, a value, or a
formula. 2. An addressable (named or numbered) storage unit
for information. A binary cell, for example, is a storage
unit that can hold 1 bit of information--that is, it can be
either on or off.
Cellular Digital Packet Data
n.
A wireless standard providing two-way, 19.2-Kbps packet data
transmission over existing cellular telephone channels.
See also packet, wireless. Acronym: CDPD.
censorship
n.
The action of preventing material that a party considers
objectionable from circulating within a system of
communication over which that party has some power. The
Internet as a whole is not censored, but some parts of it
come under varying degrees of control. A news server, for
example, often is set to exclude any or all of the alt.
newsgroups, such as alt.sex.* or alt.music.white-power,
which are unmoderated and tend to be controversial. A
moderated newsgroup or mailing list may be considered to be
"censored" because the moderator will usually delete highly
controversial and obscene content or content that is on a
different topic from that followed by the newsgroup. Online
services have identifiable owners, who often take some share
of responsibility for what reaches their users' computer
screens. In some countries, censorship of certain political
or cultural Web sites is a matter of national policy.
center
vb.
To align characters around a point located in the middle of
a line, page, or other defined area; in effect, to place
text an equal distance from each margin or border. See
also align.
centi-
prefix
1. One hundred. 2. One hundredth, as in centimeter--one
hundredth of a meter.
centralized processing
n.
The location of computer processing facilities and
operations in a single (centralized) place. Compare
decentralized processing, distributed processing.
central processing unit
n.
The computational and control unit of a computer. The
central processing unit is the device that interprets and
executes instructions. Mainframes and early minicomputers
contained circuit boards full of integrated circuits that
implemented the central processing unit. Single-chip central
processing units, called microprocessors, made
possible personal computers and workstations. Examples of
single-chip central processing units are the Motorola 68000,
68020, and 68030 chips and the Intel 8080, 8086, 80286,
80386, and i486 chips. The central processing unit--or
microprocessor, in the case of a microcomputer--has the
ability to fetch, decode, and execute instructions and to
transfer information to and from other resources over the
computer's main data-transfer path, the bus. By definition,
the central processing unit is the chip that functions as
the "brain" of a computer. In some instances, however, the
term encompasses both the processor and the computer's
memory or, even more broadly, the main computer console (as
opposed to peripheral equipment). See also
microprocessor. Acronym: CPU.
Centronics parallel interface
n.
A de facto standard for parallel data exchange paths between
computers and peripherals, originally developed by the
printer manufacturer Centronics, inc. The Centronics
parallel interface provides eight parallel data lines plus
additional lines for control and status information. See
also parallel interface.
CERN
n.
Acronym for Conseil Européen pour la Recherche Nucléaire
(the European Laboratory for Particle Physics). CERN, a
physics research center located in Geneva, Switzerland, is
where the original development of the World Wide Web took
place by Tim Berners-Lee in 1989 as a method to facilitate
communication among members of the scientific community.
See also NCSA (definition 1).
CERN server
n.
One of the first Hypertext Transfer Protocol (HTTP) servers,
developed at CERN by Tim Berners-Lee. The CERN server is
still in wide use and is free of charge. See also
CERN, HTTP server.
CERT
n.
Acronym for Computer Emergency Response Team. An
organization that provides a round-the-clock security
consultation service for Internet users and provides
advisories whenever new virus programs and other computer
security threats are discovered.
certificate
n.
A certificate is a statement guaranteeing the identity of a
person or the security of a Web site. Microsoft Internet
Explorer uses two different types of certificates: personal
certificate and Web site certificates. See digital
ID, personal certificate, Web site certificate.
certificate authority
n.
A trusted third-party organization that issues digital
certificates. See also digital ID, certificate.
certification
n.
1. The act of awarding a document to demonstrate a computer
professional's competence in a particular field. Some
hardware and software suppliers, such as Microsoft and
Novell, offer certification in the use of their products;
other organizations, such as the Institute for Certification
of Computer Professionals (ICCP) and the Computing
Technology Industry Association (CompTIA), offer more
general certification. 2. The act of awarding a document to
demonstrate that a hardware or software product meets some
specification, such as being able to work with a certain
other hardware or software product. 3. The issuance of a
notice that a user or site is trusted for the purpose of
security and computer authentication. Often certification is
used with Web sites.
CGI
n.
1. Acronym for Common Gateway Interface. 2. Acronym for
Computer Graphics Interface.
CGM
n.
Acronym for Computer Graphics Metafile.
cgi-bin
n.
Short for Common Gateway Interface-binaries. A file
directory that holds external applications to be executed by
HTTP servers via CGI. See also CGI (definition 1).
CGI script
n.
Short for Common Gateway Interface script. An external
application that is executed by an HTTP server machine in
response to a request by a client, such as a Web browser.
Generally, the CGI script is invoked when the user clicks on
some element in a Web page, such as a link or an image.
Communication between the CGI script and the server is
carried out via the CGI specification. CGI scripts can be
written in many programming languages, including C, C++, and
Visual Basic. However, the most commonly used language for
CGI scripts is Perl, because it is a small but robust
language and it is common on UNIX, which is the platform on
which the majority of Web sites run. CGI scripts don't
necessarily need to be scripts; they can also be batch
programs or compiled programs. CGI scripts are used to
provide interactivity in a Web page, including such features
as providing a form that users can fill out, image maps that
contain links to other Web pages or resources, and links
that users can click on to send e-mail to a specified
address. ActiveX controls and Java applets can provide much
the same functionality as CGI scripts, through different
means. See also CGI (definition 1), cgi-bin, image
map, Perl. Compare ActiveX controls, Java applet.
chaining
n.
In computers, the linking of two or more entities so that
they are dependent upon one another for operation. In
programming, two or more programs are said to be chained if
the first program causes the second program to begin
executing. In addition, program statements are said to be
chained if each statement, except for the first, relies on
the previous statement for input. With batch files, two or
more batch files are said to be chained if the completion of
the first batch file causes the second batch file to begin
executing. With data storage, the term chained
applies to two or more individual units of storage that are
linked together. For example, a single file on a disk may
actually be stored on several different sectors of the disk,
each of which points to the next sector containing a piece
of that file. These sectors are said to be chained together,
or, more literally, to be a chain of clusters.
Challenge Handshake
Authentication Protocol
n.
An authentication scheme used by PPP servers to validate the
identity of the originator of a connection, upon connection
or any time later. See also authentication, PPP.
Acronym: CHAP.
channel
n.
1. A path or link through which information passes between
two devices. A channel can be either internal or external to
a microcomputer. See also bus. 2. In communications,
a medium for transferring information. Depending on its
type, a communications channel can carry information (data,
sound, and/or video) in either analog or digital form. A
communications channel can be a physical link, such as the
cable connecting two stations in a network, or it can
consist of some electromagnetic transmission on one or more
frequencies within a bandwidth in the electromagnetic
spectrum, as in radio and television, or in optical,
microwave, or voice-grade communication. Also called
circuit, line. See also analog, band, bandwidth,
digital (definition 2), electromagnetic spectrum, frequency.
3. A push technology that allows users to subscribe to a Web
site to browse offline, automatically display updated pages
on their screen savers, and download or receive
notifications when pages in the Web site are modified.
Channels are available only in browsers that support channel
definitions, such as Microsoft Internet Explorer version
4.0. See also Channel Definition Format.
Channel Definition Format
n.
A specification developed by Microsoft that allows Web
publishers to deliver content from the Internet to your
computer, similar to subscribing to a favorite Web site.
channel hop
vb.
To switch repeatedly from one IRC channel to another. See
also IRC.
channel op
n.
Short for channel operator. A user on an IRC channel who has
the privilege of expelling undesirable participants. See
also IRC.
CHAP
n.
See Challenge Handshake Authentication Protocol.
character
n.
A letter, number, punctuation mark, or other symbol or
control code that is represented to a computer by one
unit--1 byte--of information. A character is not necessarily
visible, either on the screen or on paper; a space, for
example, is as much a character as is the letter a or
any of the digits 0 through 9. Because computers must manage
not only so-called printable characters but also the look
(formatting) and transfer of electronically stored
information, a character can additionally indicate a
carriage return or a paragraph mark in a word-processed
document. It can be a signal to sound a beep, begin a new
page, or mark the end of a file. See also ASCII,
control character, EBCDIC.
characteristic
n.
In mathematics, the exponent of a floating-point number (the
portion following the E that indicates the position
of the decimal point) or the integer portion of a logarithm.
See also floating-point notation, logarithm.
character map
n.
In text-based computer graphics, a block of memory addresses
that correspond to character spaces on a display screen. The
memory allocated to each character space is used to hold the
description of the character to be displayed in that space.
See also alphageometric.
character set
n.
A grouping of alphabetic, numeric, and other characters that
have some relationship in common. For example, the standard
ASCII character set includes letters, numbers, symbols, and
control codes that make up the ASCII coding scheme.
character string
n.
A set of characters treated as a unit and interpreted by a
computer as text rather than numbers. A character string can
contain any sequence of elements from a given character set,
such as letters, numbers, control characters, and extended
ASCII characters. Also called string. See also
ASCII, control character, extended ASCII.
character style
n.
Any attribute, such as boldface, italic, underline, or small
caps, applied to a character. Depending on the operating
system or program considered, the range of character styles
of text might or might not include the font, which refers to
the design of a group of characters in a given size. See
also font family.
chart
n.
A graphic or diagram that displays data or the relationships
between sets of data in pictorial rather than numeric form.
chassis
n.
A metal frame on which electronic components, such as
printed circuit boards, fans, and power supplies, are
mounted.
chat1
n.
1. Real-time conversation via computer. When a participant
types a line of text and then presses the Enter key, that
participant's words appear on the screens of the other
participants, who can then respond in kind. Most online
services support chat; on the Internet, IRC is the usual
system. See also IRC. 2. An Internet utility program
that supports chat. IRC has largely superseded it.
chat2
vb.
To carry on a real-time conversation with other users by
computer. See also IRC.
chip set
n.
A collection of chips designed to function as a unit in the
performance of some common task. The term is most commonly
used to refer to the set of integrated circuits, such as the
programmable interrupt controller, that support a CPU
together with the CPU itself. Often a chip set will fit on
one chip. See also central processing unit, chip,
integrated circuit, programmable interrupt controller.
choose
vb.
To pick a command or option from within a graphical user
interface, as by clicking a button in a dialog box or
pulling down a menu and then releasing the mouse button on
one of its options. Although select is often used
instead of choose to describe the same action,
choose is the preferred term because select has
specific connotations within computing. See also
select.
Chooser
n.
On the Apple Macintosh, a desk accessory that allows the
user to select a printer or a device on a network, such as a
file server or a printer.
Chooser extension
n.
A program that adds items to the Macintosh Chooser desk
accessory. At system startup, Chooser adds to its menu of
options from the extensions available in the system
extensions folder. For example, if you want to use a
particular printer with your Mac OS, you must have the right
Chooser extension for that printer in the extensions folder
when the computer is turned on. See also Chooser,
extension (definition 4).
cipher
n.
1. A code. 2. An encoded character. 3. A zero.
circuit
n.
1. Any path that can carry electrical current. 2. A
combination of electrical components interconnected to
perform a particular task. At one level, a computer consists
of a single circuit; at another, it consists of hundreds of
interconnected circuits.
circuit analyzer
n.
Any device for measuring one or more characteristics of an
electrical circuit. Voltage, current, and resistance are the
characteristics most commonly measured. Oscilloscopes are
circuit analyzers.
circuit board
n.
A flat piece of insulating material, such as epoxy or
phenolic resin, on which electrical components are mounted
and interconnected to form a circuit. Most modern circuit
boards use patterns of copper foil to interconnect the
components. The foil layers may be on one or both sides of
the board and, in more advanced designs, in several layers
within the board. A printed circuit board is one in which
the pattern of copper foil is laid down by a printing
process such as photolithography. See also board,
printed circuit board.
circuit breaker
n.
A switch that opens and cuts off the flow of current when
the current exceeds a certain level. Circuit breakers are
placed at critical points in circuits to protect against
damage that could result from excessive current flow, which
is typically caused by component failure. Circuit breakers
are often used in place of fuses because they need only to
be reset rather than replaced. Compare surge
protector.
CISC
n.
Acronym for complex instruction set computing. The
implementation of complex instructions in a microprocessor
design so that they can be invoked at the assembly language
level. The instructions can be very powerful, allowing for
complicated and flexible ways of calculating such elements
as memory addresses. All this complexity, however, usually
requires many clock cycles to execute each instruction.
Compare RISC.
class
n.
In object-oriented programming, a generalized category that
describes a group of more specific items, called objects,
that can exist within it. A class is a descriptive tool used
in a program to define a set of attributes or a set of
services (actions available to other parts of the program)
that characterize any member (object) of the class. Program
classes are comparable in concept to the categories that
people use to organize information about their world, such
as animal, vegetable, and mineral, that define
the types of entities they include and the ways those
entities behave. The definition of classes in
object-oriented programming is comparable to the definition
of types in languages such as C and Pascal. See also
object-oriented programming.
Class A network
n.
An Internet network that can define a maximum of 16,777,215
hosts. Class A networks use the first byte of an IP address
to designate the network, with the first (high-order) bit
set to 0. The host is designated by the last 3 bytes. Class
A addressing currently allows for a maximum of 128 networks.
Class A networks are best suited for sites with few networks
but numerous hosts and are usually designated for use by
large government or educational institutions. See also
host, IP address.
classless interdomain routing
n.
An address scheme that uses aggregation strategies to
minimize the size of top-level Internet routing tables.
Routes are grouped with the objective of minimizing the
quantity of information carried by core routers. The main
requirement for this scheme is the use of routing protocols
that support it, such as Border Gateway Protocol (BGP)
Version 4 and RIP Version 2. See also Border Gateway
Protocol, communications protocol, RIP, router. Acronym:
CIDR.
clean boot
n.
Booting or starting a computer using the minimum system
files in the operating system. The clean boot is used as a
troubleshooting method for isolating problems associated
with software that may be calling on the same system
resources at the same time, causing conflicts that lower the
performance of the system, make some programs inoperable, or
crash the computer. See also boot1, crash2
(definition 1), operating system.
clean install
n.
Reinstallation of software in a manner that ensures that no
application or system files from a previous installation
will remain. The procedure prevents "smart" installer
programs from skipping file installations where a file
already exists, which could potentially keep a problem from
being removed.
Clear key
n.
A key in the upper left corner of the numeric keypad on some
keyboards. In many applications, it clears the currently
selected menu choice or deletes the current selection.
click
vb.
To press and release a mouse button once without moving the
mouse. Clicking is usually performed to select or deselect
an item or to activate a program or program feature. See
also right click. Compare double-click, drag.
click speed
n.
The maximum interval between the first and second time a
user presses a button on a mouse or other pointing device
that will still identify these actions as a double-click to
the computer as opposed to two single-clicks. See also
double-click, mouse, pointing device.
client
n.
1. In object-oriented programming, a member of a class
(group) that uses the services of another class to which it
is not related. See also inheritance (definition 1).
2. A process, such as a program or task, that requests a
service provided by another program--for example, a word
processor that calls on a sort routine built into another
program. The client process uses the requested service
without having to "know" any working details about the other
program or the service itself. Compare child
(definition 1), descendant (definition 2). 3. On a local
area network or the Internet, a computer that accesses
shared network resources provided by another computer
(called a server). See also client/server
architecture, server.
client error
n.
A problem reported by the Hypertext Transfer Protocol (HTTP)
client module as the result of difficulty in interpreting a
command or the inability to connect properly to a remote
host.
client/server architecture
n.
An arrangement used on local area networks that makes use of
distributed intelligence to treat both the server and the
individual workstations as intelligent, programmable
devices, thus exploiting the full computing power of each.
This is done by splitting the processing of an application
between two distinct components: a "front-end" client and a
"back-end" server. The client component is a complete,
stand-alone personal computer (not a "dumb" terminal), and
it offers the user its full range of power and features for
running applications. The server component can be a personal
computer, a minicomputer, or a mainframe that provides the
traditional strengths offered by minicomputers and
mainframes in a time-sharing environment: data management,
information sharing between clients, and sophisticated
network administration and security features. The client and
server machines work together to accomplish the processing
of the application being used. Not only does this increase
the processing power available over older architectures but
it also uses that power more efficiently. The client portion
of the application is typically optimized for user
interaction, whereas the server portion provides the
centralized, multiuser functionality. See also
distributed intelligence.
client-side image maps
n.
A Web page user selection device whereby regions of an image
can be clicked with the mouse to indicate user selections
from a presented collection of options, comparable to
clicking an icon of the desired item on a menu. Unlike the
earliest Web implementation of image maps (circa 1993),
client-side image maps do not transmit the mouse click
coordinates to the Web server for processing but perform the
processing completely within the client program (i.e., Web
browser) itself, generally improving the speed of response
to the user. See also image map.
client-side program
n.
On the Internet, a program that is run on a client computer
rather than on a server computer. Client-side programs do
not communicate over the Internet.
clip
vb.
1. To cut off the portion of a displayed image that lies
beyond a certain boundary, such as the edge of a window.
Certain graphics programs also support clipping as a means
of masking everything but a certain object so that painting
tools, for example, can be applied to the object alone. 2.
To cut a photograph, drawing, or other illustrations from a
clip art collection--either in a book or on a disk. See
also clip art. 3. To cut off the peaks of a signal in an
electronic circuit.
clip art
n.
A collection--either in a book or on a disk--of proprietary
or public-domain photographs, diagrams, maps, drawings, and
other such graphics that can be "clipped" from the
collection and incorporated into other documents.
clipboard
n.
1. A special memory resource maintained by windowing
operating systems. The clipboard stores a copy of the last
information that was "copied" or "cut." A "paste" operation
passes data from the clipboard to the current program. A
clipboard allows information to be transferred from one
program to another, provided the second program can read
data generated by the first. Data copied using the clipboard
is static and will not reflect later changes. See also
cut and paste, DDE. Compare scrap. 2. A computer that
uses a pen as the primary input device. See also
clipboard computer, pen computer.
Clipper Chip
n.
An integrated circuit that implements the SkipJack
algorithm, an encryption algorithm created by the National
Security Agency that encrypts 64-bit blocks of data with an
80-bit key. The Clipper is manufactured by the U.S.
government to encrypt telephone data. It has the added
feature that it can be decrypted by the U.S. government,
which has tried unsuccessfully to make the chip compulsory
in the United States. See also encryption.
clipping path
n.
A polygon or curve that is used to mask an area in a
document. Only what is inside the clipping path appears when
the document is printed. See also PostScript.
clock
n.
1. The electronic circuit in a computer that generates a
steady stream of timing pulses--the digital signals that
synchronize every operation. The system clock signal is
precisely set by a quartz crystal, typically at a specific
frequency between 1 and 50 megahertz. The clock rate of a
computer is one of the prime determinants of its overall
processing speed, and it can go as high as the other
components of the computer allow. Also called system
clock. 2. The battery-backed circuit that keeps track of the
time and date in a computer--not the same as the system
clock. Also called clock/calendar.
clock/calendar
n.
An independent timekeeping circuit used within a
microcomputer to maintain the correct time and calendar
date. A clock/calendar circuit is battery powered, so it
continues running even when the computer is turned off. The
time and date kept by the clock/calendar can be used by the
operating system (for example, to "stamp" files with the
date and time of creation or revision) and by application
programs (for example, to insert the date or time in a
document). Also called clock, internal clock.
clock doubling
n.
A technology employed by some Intel microprocessors that
enables the chip to process data and instructions at twice
the speed of the rest of the system. See also
i486DX2.
clock rate
n.
The rate at which the clock in an electronic device, such as
a computer, oscillates. The clock rate is normally given in
hertz (Hz, one cycle per second), kilohertz (kHz, one
thousand cycles per second), or megahertz (MHz, one million
cycles per second). Clock rates in personal computers
increased from about 5 MHz to about 50 MHz between 1981 and
1995. Also called clock speed, hertz time. See
also clock (definition 1).
clone
n.
A copy; in microcomputer terminology, a look-alike,
act-alike computer that contains the same microprocessor and
runs the same programs as a better-known, more prestigious,
and often more expensive machine.
close1
n.
An FTP command that instructs the client to close the
current connection with a server. See also FTP1
(definition 1), Web site.
close2
vb.
1. To end an application's relationship with an open file so
that the application will no longer be able to access the
file without opening it again. 2. To end a computer's
connection with another computer on a network.
close box
n.
In the Macintosh graphical user interface, a small box in
the left corner of a window's title bar. Clicking on the box
closes the window. Compare close button.
close button
n.
In the graphical user interface for Windows 95, Windows NT,
and the X Window System, a square button in the right corner
(left corner in X Windows) of a window's title bar with an ×
mark on it. Clicking on the button closes the window.
Also called X button. Compare close box.
closed architecture
n.
1. Any computer design whose specifications are not freely
available. Such proprietary specifications make it difficult
or impossible for third-party vendors to create ancillary
devices that work correctly with a closed-architecture
machine; usually only its original maker can build
peripherals and add-ons for such a machine. Compare
open architecture (definition 1). 2. A computer system that
provides no expansion slots for adding new types of circuit
boards within the system unit. The original Apple Macintosh
was an example of a closed architecture. Compare open
architecture (definition 2).
cluster
n.
1. An aggregation, such as a group of data points on a
graph. 2. A communications computer and its associated
terminals. 3. In data storage, a disk-storage unit
consisting of a fixed number of sectors (storage segments on
the disk) that the operating system uses to read or write
information; typically, a cluster consists of two to eight
sectors, each of which holds a certain number of bytes
(characters).
CMOS
n.
1. Acronym for complementary metal-oxide semiconductor. A
semiconductor technology in which pairs of metal-oxide
semiconductor field effect transistors (MOSFETs), one N-type
and the other P-type, are integrated on a single silicon
chip. Generally used for RAM and switching applications,
these devices have very high speed and extremely low power
consumption. They are, however, easily damaged by static
electricity. See also MOSFET, N-type semiconductor,
P-type semiconductor. 2. The battery-backed memory
(presumably made with complementary metal-oxide
semiconductor technology) used to store parameter values
needed to boot IBM Personal Computers and compatibles, such
as the type of disks and the amount of memory, as well as
the clock/calendar time.
CMOS RAM
n.
Random access memory made using complementary metal-oxide
semiconductor technology. CMOS chips consume extremely
little power and have high tolerance for noise from the
power supply. These characteristics make CMOS chips,
including CMOS RAM chips, very useful in hardware components
that are powered by batteries, such as most microcomputer
clocks and certain types of scratchpad RAM that are
maintained by the operating system. See also CMOS
(definition 1), parameter RAM, RAM.
CMOS setup
n.
A system configuration utility, accessible at boot time, for
setting up certain system options, such as the date and
time, the kind of drives installed, and port configuration.
See also CMOS (definition 2).
CMY
n.
Acronym for cyan-magenta-yellow. A model for describing
colors that are produced by absorbing light, as by ink on
paper, rather than by emitting light, as on a video monitor.
The three kinds of cone cells in the eye respond to red,
green, and blue light, which are absorbed (removed from
white light) by cyan, magenta, and yellow pigments,
respectively. Percentages of pigments in these subtractive
primary colors can therefore be mixed to get the appearance
of any desired color. Absence of any pigment leaves white
unchanged; adding 100 percent of all three pigments turns
white to black. Compare CMYK, RGB.
CMYK
n.
Acronym for cyan-magenta-yellow-black. A color model that is
similar to the CMY color model but produces black with a
separate black component rather than by adding 100 percent
of cyan, magenta, and yellow. See also CMY.
coaxial cable
n.
A two-conductor cable consisting of a center wire inside a
grounded cylindrical shield, typically made of braided wire,
that is insulated from the center wire. The shield prevents
signals transmitted on the center wire from affecting nearby
components and prevents external interference from affecting
the signal carried on the center wire.
code1
n.
1. Program instructions. Source code consists of
human-readable statements written by a programmer in a
programming language. Machine code consists of numerical
instructions that the computer can recognize and execute and
that were converted from source code. See also data,
program. 2. A system of symbols used to convert information
from one form to another. A code for converting information
in order to conceal it is often called a cipher. 3.
One of a set of symbols used to represent information.
code2
vb.
To write program instructions in a programming language.
See also program.
codec
n.
1. Short for coder/decoder. Hardware that can convert audio
or video signals between analog and digital forms. 2. Short
for compressor/decompressor. Hardware or software that can
compress and uncompress audio or video data. See also
compress2, uncompress. 3. Hardware that combines
the functions of definitions 1 and 2.
cold boot
n.
A startup process that begins with turning on the computer's
power. Typically, a cold boot involves some basic hardware
checking by the system, after which the operating system is
loaded from disk into memory. See also boot1.
Compare warm boot.
collate
vb.
In data handling, to merge items from two or more similar
sets to create a combined set that maintains the order or
sequence of items in the original sets.
collision
n.
The result of two devices or network workstations trying to
transmit signals at the exact same time on the same channel.
The typical outcome is a garbled transmission.
collision detection
n.
1. The process by which a node on a local area network
monitors the communications line to determine when a
collision has occurred; that is, when two nodes have
attempted to transmit at the same time. Although network
stations usually avoid collisions by monitoring the line and
waiting for it to clear before transmitting, the method is
not foolproof. When a collision does occur, the two nodes
involved usually wait a random amount of time before
attempting to retransmit. See also contention,
CSMA/CD. 2. The process by which a game or simulation
program determines whether two objects on the screen are
touching each other. This is a time-consuming, often
complicated procedure; some computers optimized for graphics
and games, such as the Amiga, have special hardware built in
specifically to detect collisions.
color
n.
In physics, the component of the human perception of light
that depends on frequency. For light of a single frequency,
color ranges from violet at the high-frequency end of the
visible-light band (a small portion of the total
electromagnetic spectrum) to red at the low-frequency end.
In computer video, color is produced by a combination of
hardware and software. Software manipulates combinations of
bits that represent the distinct shades of color that are
destined for particular positions on the screen (characters
or individual dots, called pixels). The video adapter
hardware translates these bits into electrical signals,
which in turn control the brightnesses of different-colored
phosphors at the corresponding positions on the screen of
the monitor CRT. The user's eye unites the light from the
phosphors to perceive a single color. See also color
model, color monitor, CRT, HSB, monitor, RGB, video, video
adapter.
color bits
n.
A predetermined number of bits assigned to each displayable
pixel that determine its color when it is displayed on a
monitor. For example, two color bits are required for four
colors; eight color bits are required for 256 colors. See
also pixel image. Compare bit plane.
color box
n.
In the Microsoft NT and Windows 95 Paint accessory, a
graphic screen element in the form of a paint box that is
used to select foreground and background colors.
color management
n.
In printing, the process of producing accurate, consistent
color using any of a variety of output devices. Color
management includes accurate conversion of RGB input from a
scanner, camera, or monitor to CMYK output for a printer;
application of a device profile for the printer or other
output device on which the image will be reproduced; and
allowance for environmental variations such as humidity and
barometric pressure. See also CMYK, RGB.
color management system
n.
A technology developed by Kodak and licensed to many other
software vendors that is designed to calibrate and match
colors that appear on video monitors and computer monitors
and those that appear in any printed form. Acronym:
CMS.
color printer
n.
A computer printer that can print full-color output. Most
color printers can also produce black-and-white output.
color saturation
n.
The amount of a hue contained in a color; the more
saturation, the more intense the color. See also
color model, HSB.
color scanner
n.
A scanner that converts images to a digitized format and is
able to interpret color. Depth of color depends on the
scanner's bit depth--its ability to transform color into 8,
16, 24, or 32 bits. High-end color scanners, commonly used
when output is to be printed, are able to encode information
at a high resolution or number of dots per inch (dpi).
Low-end color scanners encode information at a resolution of
72 dpi and are commonly used for computer screen images not
intended for printing. See also resolution
(definition 1), scanner.
column
n.
1. A series of items arranged vertically within some type of
framework--for example, a continuous series of cells running
from top to bottom in a spreadsheet, a set of lines of
specified width on a printed page, a vertical line of pixels
on a video screen, or a set of values aligned vertically in
a table or matrix. Compare row. 2. In a relational
database management system, the name for an attribute. The
collection of column values that form the description of a
particular entity is called a tuple or row. A
column is equivalent to a field in a record in a
nonrelational file system. See also entity, field
(definition 1), row, table (definition 2).
column chart
n.
A bar chart in which values are displayed and printed as
vertical bars. See also bar chart.
COM
n.
1. A name reserved by the MS-DOS operating system for serial
communications ports. For example, if a modem is connected
to one serial port and a serial printer to another, the
devices are identified as COM1 and COM2 by the operating
system. 2. Acronym for Component Object Model. A
specification developed by Microsoft for building software
components that can be assembled into programs or add
functionality to existing programs running on Microsoft
Windows platforms. COM components can be written in a
variety of languages, although most are written in C++, and
can be unplugged from a program at run time without having
to recompile the program. COM is the foundation of the OLE
(object linking and embedding), ActiveX, and DirectX
specifications. See also ActiveX, component
(definition 2), DirectX, OLE. 3. The extension reserved by
MS-DOS for a type of executable binary (program) file
limited to a single 64-kilobyte (KB) segment. COM files are
often used for utility programs and short routines. They are
not supported in OS/2. 4. Acronym for computer-output
microfilm. Microfilm that can record data from a computer.
COM1
n.
A serial communications port in Wintel systems. COM1 is
usually specified by the I/O range 03F8H, is usually
associated with interrupt request line IRQ4, and in many
systems is used to connect an RS232 serial mouse. See
also IRQ.
COM2
n.
A serial communications port in Wintel systems. COM2 is
usually specified by the I/O range 02F8H, is usually
associated with interrupt request line IRQ3, and in many
systems is used to connect a modem. See also IRQ.
COM3
n.
A serial communications port in Wintel systems. COM3 is
usually specified by the I/O range 03E8H, is usually
associated with interrupt request line IRQ4, and in many
systems is used as an alternative to COM1 or COM2 if the
latter is being used by some other peripheral. See also
IRQ.
COMDEX
n.
Any of a series of annual computer trade shows operated by
Softbank COMDEX,Inc. One of these shows takes place in Las
Vegas each November and is the largest computer trade show
in the United States.
Comité Consultatif International
Télégraphique et Téléphonique
n.
Also called International Telegraph and Telephone
Consultative. See CCITT.
comma-delimited file
n.
A data file consisting of fields and records, stored as
text, in which the fields are separated from each other by
commas. Use of comma-delimited files allows communication
between database systems that use different formats. If the
data in a field contains a comma, the field is further
surrounded with quotation marks.
command
n.
An instruction to a computer program that, when issued by
the user, causes an action to be carried out. Commands are
usually either typed at the keyboard or chosen from a menu.
COMMAND.COM
n.
The command interpreter for MS-DOS. See also command
interpreter.
command-driven
adj.
Accepting commands in the form of code words or letters,
which the user must learn. Compare menu-driven.
command interpreter
n.
A program, usually part of the operating system, that
accepts typed commands from the keyboard and performs tasks
as directed. The command interpreter is responsible for
loading applications and directing the flow of information
between applications. In OS/2 and MS-DOS, the command
interpreter also handles simple functions, such as moving
and copying files and displaying disk directory information.
See also shell1.
Command key
n.
On the original Macintosh keyboard, a key labeled with the
special symbol, sometimes called the propeller or puppy
foot. This key is found on one or both sides of the
Spacebar, depending on the version of the Apple keyboard.
The key serves some of the same functions as the Control key
on IBM keyboards. See also Control key.
command line
n.
A string of text written in the command language and passed
to the command interpreter for execution. See also
command language.
comment
n.
Text embedded in a program for documentation purposes.
Comments usually describe what the program does, who wrote
it, why it was changed, and so on. Most programming
languages have a syntax for creating comments so that they
can be recognized and ignored by the compiler or assembler.
Also called remark. See also comment out.
comment out
vb.
To disable one or more lines of code from a program
temporarily by enclosing them within a comment statement.
See also comment, conditional compilation, nest.
commerce server
n.
An HTTP server designed for conducting online business
transactions. Data is transferred between the server and Web
browser in an encrypted form to help protect information
such as credit card numbers. Commerce servers are typically
used by online stores and companies that are set up for mail
order business. The wares or services offered by the store
or company are described and displayed in photographs on the
store or company Web site, and users can order
directly from the site, using their Web browser. A
number of companies market commerce servers, including
Netscape, Microsoft, and Quarterdeck. See
also HTTP server (definition 1), Secure Sockets
Layer, Web browser.
Commercial Internet Exchange
n.
A non-profit trade organization of public Internet service
providers. In addition to the usual representational and
social activities, CIX also operates an Internet backbone
router that is accessible to its members. See also
backbone (definition 1), ISP, router. Acronym: CIX.
Common Access Method
n.
A standard developed by Future Domain and other SCSI vendors
allowing SCSI adapters to communicate with SCSI peripherals
regardless of the particular hardware used. See also
SCSI.
common carrier
n.
A communications company (e.g., a telephone company) that
provides service to the public and is regulated by
governmental organizations.
Common Gateway Interface
n.
The specification that defines communications between
information servers (such as HTTP servers) and resources on
the server's host computer, such as databases and other
programs. For example, when a user submits a form through a
Web browser, the HTTP server executes a program (often
called a CGI script) and passes the user's input information
to that program via CGI. The program then returns
information to the server via CGI. Use of CGI can make a Web
page much more dynamic and add interactivity for the user.
See also CGI script, HTTP server.
n.
Acronym CGI. A software standard applied to computer
graphics devices, such as printers and plotters. Computer
Graphics Interface is an offshoot of a widely recognized
graphics standard called GKS (Graphical Kernel System),
which provides applications programmers with standard
methods of creating, manipulating, and displaying or
printing computer graphics. See also Graphical Kernel
System.
Common Hardware Reference
Platform
n.
A specification describing a family of machines, based on
the PowerPC processor, that are capable of booting multiple
operating systems, including Mac OS, Windows NT, AIX, and
Solaris. See also PowerPC. Acronym: CHRP.
n.
A standard proposed by Microsoft that would compete directly
with Sun Microsystems' Web Network File System. A system of
file sharing of Internet or intranet files. Acronym:
CIFS.
communications
n.
The vast discipline encompassing the methods, mechanisms,
and media involved in information transfer. In
computer-related areas, communications involves data
transfer from one computer to another through a
communications medium, such as a telephone, microwave relay,
satellite link, or physical cable. Two primary methods of
computer communications exist: temporary connection of two
computers through a switched network, such as the public
telephone system, and permanent or semipermanent linking of
multiple workstations or computers in a network. The line
between the two is indistinct, however, because
microcomputers equipped with modems are often used to access
both privately owned and public-access network computers.
See also asynchronous transmission, CCITT, channel
(definition 2), communications protocol, IEEE, ISDN, ISO/OSI
model, LAN, modem, network, synchronous transmission.
Compare data transmission, telecommunications,
teleprocess.
communications controller
n.
A device used as an intermediary in transferring
communications to and from the host computer to which it is
connected. By relieving the host computer of the actual
tasks of sending, receiving, deciphering, and checking
transmissions for errors, a communications controller helps
to make efficient use of the host computer's processing
time--time that might be better used for noncommunications
tasks. A communications controller can be either a
programmable machine in its own right or a nonprogrammable
device designed to follow certain communications protocols.
See also front-end processor (definition 2).
communications link
n.
The connection between computers that enables data transfer.
communications program
n.
A software program that enables a computer to connect with
another computer and to exchange information. For initiating
communications, communications programs perform such tasks
as maintaining communications parameters, storing and
dialing phone numbers automatically, recording and executing
logon procedures, and repeatedly dialing busy lines. Once a
connection is made, communications programs can also be
instructed to save incoming messages on disk or to find and
transmit disk files. During communication, these types of
programs perform the major, and usually invisible, tasks of
encoding data, coordinating transmissions to and from the
distant computer, and checking incoming data for
transmission errors.
communications protocol
n.
A set of rules or standards designed to enable computers to
connect with one another and to exchange information with as
little error as possible. The protocol generally accepted
for standardizing overall computer communications is a
seven-layer set of hardware and software guidelines known as
the OSI (Open Systems Interconnection) model. A somewhat
different standard, widely used before the OSI model was
developed, is IBM's SNA (Systems Network Architecture). The
word protocol is often used, sometimes confusingly,
in reference to a multitude of standards affecting different
aspects of communication, such as file transfer (for
example, XMODEM and ZMODEM), handshaking (for example,
XON/XOFF), and network transmissions (for example, CSMA/CD).
See also ISO/OSI model, SNA.
communications satellite
n.
A satellite stationed in geosynchronous orbit that acts as a
microwave relay station, receiving signals sent from a
ground-based station (earth station), amplifying them, and
retransmitting them on a different frequency to another
ground-based station. Initially used for telephone and
television signals, communications satellites can also be
used for high-speed transmission of computer data. Two
factors affecting the use of satellites with computers,
however, are propagation delay (the time lag caused by the
distance traveled by the signal) and security concerns.
See also downlink, uplink.
communications server
n.
A gateway that translates packets on a local area network
(LAN) into asynchronous signals, such as those used on
telephone lines or in RS-232-C serial communications, and
allows all nodes on the LAN access to its modems or RS-232-C
connections. See also gateway, RS-232-C standard.
communications slot
n.
On many models of the Apple Macintosh, a dedicated expansion
slot for network interface cards. Acronym: CS.
communications software
n.
The software that controls the modem in response to user
commands. Generally such software includes terminal
emulation as well as file transfer facilities. See also
modem, terminal emulation.
communications system
n.
The combination of hardware, software, and data transfer
links that make up a communications facility.
compact disc
n.
1. An optical storage medium for digital data, usually
audio. A compact disc is a nonmagnetic, polished metal disc
with a protective plastic coating that can hold up to 74
minutes of high-fidelity recorded sound. The disk is read by
an optical scanning mechanism that uses a high-intensity
light source, such as a laser, and mirrors. Also called
optical disc. 2. A technology that forms the basis of media
such as CD-ROM, CD-ROM/XA, CD-I, CD-R, DVI, and PhotoCD.
These media are all compact disc-based but store
various types of digital information and have different
read/write capabilities. Documentation for compact disc
formats can be found in books designated by the color of
their covers. For example, documentation for audio compact
discs is found in the Red Book. See also CD-I, CD-R,
CD-ROM, CD-ROM/XA, DVI, Green Book (definition 2), Orange
Book (definition 2), PhotoCD, Red Book. Acronym: CD.
compact disc-erasable
n.
A technological improvement in compact discs whereby
information can be repeatedly changed on the CD.
Contemporary CDs are "write once, read many," in that the
information originally written cannot be changed, but can
only be appended to. Acronym: CD-E.
compact disc player
n.
A device that reads the information stored on a compact
disc. A compact disc player contains the optical equipment
necessary for reading a disc's contents and the electronic
circuitry for interpreting the data as it is read.
compare
vb.
To check two items, such as words, files, or numeric values,
so as to determine whether they are the same or different.
In a program, the outcome of a compare operation often
determines which of two or more actions is taken next.
compatibility
n.
1. The degree to which a computer, an attached device, a
data file, or a program can work with or understand the same
commands, formats, or language as another. True
compatibility means that any operational differences are
invisible to people and programs alike. 2. The extent to
which two machines can work in harmony. Compatibility (or
the lack thereof) between two machines indicates whether,
and to what degree, the computers can communicate, share
data, or run the same programs. For example, an Apple
Macintosh and an IBM PC are generally incompatible because
they cannot communicate freely or share data without the aid
of hardware and/or software that functions as an
intermediary or a converter. 3. The extent to which a piece
of hardware conforms to an accepted standard (for example,
IBM-compatible or Hayes-compatible). In this sense,
compatibility means that the hardware ideally operates in
all respects like the standard on which it is based. 4. In
reference to software, harmony on a task-oriented level
among computers and computer programs. Computers deemed
software-compatible are those that can run programs
originally designed for other makes or models. Software
compatibility also refers to the extent to which programs
can work together and share data. In another area, totally
different programs, such as a word processor and a drawing
program, are compatible with one another if each can
incorporate images or files created using the other. All
types of software compatibility become increasingly
important as computer communications, networks, and
program-to-program file transfers become near-essential
aspects of microcomputer operation. See also downward
compatibility, upward-compatible.
compatibility mode
n.
A mode in which hardware or software in one system supports
operations of software from another system. The term often
refers to the ability of advanced operating systems designed
for Intel microprocessors (for example, OS/2 and Windows NT)
to run MS-DOS software or to the ability of some UNIX
workstations and of some Apple Macintosh systems to run
MS-DOS software.
compile
vb.
To translate all the source code of a program from a
high-level language into object code prior to execution of
the program. Object code is executable machine code or a
variation of machine code. More generally, compiling
is sometimes used to describe translating any high-level
symbolic description into a lower-level symbolic or
machine-readable format. A program that performs this task
is known as a compiler. See also compiler,
compile time, high-level language, machine code, source
code. Compare interpret.
compiler
n.
1. Any program that transforms one set of symbols into
another by following a set of syntactic and semantic rules.
2. A program that translates all the source code of a
program written in a high-level language into object code
prior to execution of the program. See also
assembler, compile, high-level language, interpreted
language, language processor, object code.
comp. newsgroups
n.
Usenet newsgroups that are part of the comp. hierarchy and
have the prefix comp. These newsgroups are devoted to
discussions of computer hardware, software, and other
aspects of computer science. Comp. newsgroups are one of the
seven original Usenet newsgroup hierarchies. The other six
are misc., news., rec., sci., soc., and talk. See also
newsgroup, traditional newsgroup hierarchy, Usenet.
component
n.
1. A discrete part of a larger system or structure. 2. An
individual modular software routine that has been compiled
and dynamically linked, and is ready to use with other
components or programs. See also compile, component
software, link (definition 1), program, routine.
COM port
or comm port n. Short for
communications port, the logical address assigned by MS-DOS
(versions 3.3 and higher) and Microsoft Windows (including
Windows 95 and Windows NT) to each of the four serial ports
on an IBM Personal Computer or a PC compatible. COM ports
also have come to be known as the actual serial ports on a
PC's CPU where peripherals, such as printers, scanners, and
external modems, are plugged in. See also COM
(definition 1), input/output port, serial port.
compress1
n.
A proprietary UNIX utility for reducing the size of data
files. Files compressed with this utility have the extension
.Z added to their names.
compress2
vb.
To reduce the size of a set of data, such as a file or a
communications message, so that it can be stored in less
space or transmitted with less bandwidth. Data can be
compressed by removing repeated patterns of bits and
replacing them with some form of summary that takes up less
space; restoring the repeated patterns decompresses the
data. Lossless compression methods must be used for text,
code, and numeric data files; lossy compression may be used
for video and sound files. See also lossless
compression, lossy compression.
compressed disk
n.
A hard disk or floppy disk whose apparent capacity to hold
data has been increased through the use of a compression
utility, such as Stacker or Double Space. See also
data compression.
compressed drive
n.
A hard disk whose apparent capacity has been increased
through the use of a compression utility, such as Stacker or
Double Space. See also compressed disk, data
compression.
compressed file
n.
A file whose contents have been compressed by a special
utility program so that it occupies less space on a disk or
other storage device than in its uncompressed (normal)
state. See also installation program, LHARC, PKUNZIP,
PKZIP, utility program.
CompuServe
n.
An online information service that provides information and
communications capabilities, including Internet access. It
is primarily known for its technical support forums for
commercial hardware and software products and for being one
of the first large commericial online services. CompuServe
also operates various private network services.
compute
vb.
1. To perform calculations. 2. To use a computer or cause it
to do work.
computer
n.
Any machine that does three things: accepts structured
input, processes it according to prescribed rules, and
produces the results as output. Ways to categorize computers
are described in the table. See also analog, digital,
integrated circuit, large-scale integration,
very-large-scale integration.
k:\compdict\database\4128.doc
computer-aided design and
drafting
n.
A system of hardware and software similar to CAD but with
additional features related to engineering conventions,
including the ability to display dimension specifications
and other notes. See also CAD. Acronym: CADD.
computer art
n.
A broad term that can refer either to art created on a
computer or to art generated by a computer, the difference
being whether the artist is human or electronic. When
created by human beings, computer art is done with painting
programs that offer a range of line-drawing tools, brushes,
shapes, patterns, and colors. Some programs also offer
predrawn figures and animation capabilities.
computer-assisted learning
n.
The use of computers and their multimedia abilities to
present information for educational purposes.
computer center
n.
A centralized location that contains computers, such as
mainframes or minicomputers, along with associated equipment
for providing data processing services to a group of people.
computer crime
n.
The illegal use of a computer by an unauthorized individual,
either for pleasure (as by a computer hacker) or for profit
(as by a thief). See also hacker (definition 2).
computer game
n.
A class of computer program in which one or more users
interact with the computer as a form of entertainment.
Computer games run the gamut from simple alphabet games for
toddlers to chess, treasure hunts, war games, and
simulations of world events. The games are controlled from a
keyboard or with a joystick or other device and are supplied
on disks, on CD-ROMs, as game cartridges, or as arcade
devices.
computer graphics
n.
The display of "pictures," as opposed to only alphabetic and
numeric characters, on a computer screen. Computer graphics
encompasses different methods of generating, displaying, and
storing information. Thus, computer graphics can refer to
the creation of business charts and diagrams; the display of
drawings, italic characters, and mouse pointers on the
screen; or the way images are generated and displayed on the
screen. See also graphics mode, presentation
graphics, raster graphics, vector graphics.
Computer Graphics Interface
n.
A software standard applied to computer graphics devices,
such as printers and plotters. Computer Graphics Interface
is an offshoot of a widely recognized graphics standard
called GKS (Graphical Kernel System), which provides
applications programmers with standard methods of creating,
manipulating, and displaying or printing computer graphics.
See also Graphical Kernel System. Acronym:
CGI.
Computer Graphics Metafile
n.
A software standard related to the widely recognized GKS
(Graphical Kernel System) that provides applications
programmers with a standard means of describing a graphic as
a set of instructions for re-creating it. A graphics
metafile can be stored on disk or sent to an output device;
Computer Graphics Metafile provides a common language for
describing such files in relation to the GKS standard.
See also Graphical Kernel System. Acronym: CGM.
computer literacy
n.
Knowledge and an understanding of computers combined with
the ability to use them effectively. On the least
specialized level, computer literacy involves knowing how to
turn on a computer, start and stop simple application
programs, and save and print information. At higher levels,
computer literacy becomes more detailed, involving the
ability of power users to manipulate complex applications
and, possibly, to program in languages such as Basic or C.
At the highest levels, computer literacy leads to
specialized technical knowledge of electronics and assembly
language. See also power user.
computer name
n.
In computer networking, a name that uniquely identifies a
computer to the network. A computer's name cannot be the
same as any other computer or domain name on the network. It
differs from a user name in that the computer name is used
to identify a particular computer and all its shared
resources to the rest of the system so that they can be
accessed. Compare alias (definition 2), user name.
computerphile
n.
A person who is immersed in the world of computing, who
collects computers, or whose hobby involves computing.
computer revolution
n.
The societal and technological phenomenon involving the
swift development and widespread use and acceptance of
computers--specifically single-user personal computers. The
impact of these machines is considered revolutionary for two
reasons. First, their appearance and success were rapid.
Second, and more important, their speed and accuracy
produced a change in the ways in which information can be
processed, stored, and transferred.
computer science
n.
The study of computers, including their design, operation,
and use in processing information. Computer science combines
both theoretical and practical aspects of engineering,
electronics, information theory, mathematics, logic, and
human behavior. Aspects of computer science range from
programming and computer architecture to artificial
intelligence and robotics.
computer security
n.
The steps taken to help protect a computer and the
information it contains. On large systems or those handling
financial or confidential data, helping protect
computer security requires professional supervision that
combines legal and technical expertise. On a
microcomputer, users can help protect their data by
backing up and storing copies of files in a separate
location, and the integrity of data on the computer
can be maintained by assigning passwords to files,
marking files "read-only" to avoid changes to them,
physically locking a hard disk, storing sensitive
information on floppy disks kept in locked cabinets,
and installing special programs to help protect against
viruses. On a computer to which many people have
access, security can be enhanced by requiring
personnel to use passwords and by granting only approved
users access to sensitive information. See also
bacterium, encryption, virus.
CON
n.
The logical device name for console; reserved by the
MS-DOS operating system for the keyboard and the screen. The
input-only keyboard and the output-only screen together make
up the console and represent the primary sources of input
and output in an MS-DOS computer system.
concurrent
adj.
Of, pertaining to, or characteristic of a computer operation
in which two or more processes (programs) have access to the
microprocessor's time and are therefore carried out nearly
simultaneously. Because a microprocessor can work with much
smaller units of time than people can perceive, concurrent
processes appear to be occurring simultaneously but in
reality are not.
concurrent execution
n.
The apparently simultaneous execution of two or more
routines or programs. Concurrent execution can be
accomplished on a single process or by using time-sharing
techniques, such as dividing programs into different tasks
or threads of execution, or by using multiple processors.
Also called parallel execution. See also parallel
algorithm, processor, sequential execution, task, thread
(definition 1), time-sharing.
condensed
adj.
Of, pertaining to, or characteristic of a font style,
supported in some applications, that reduces the width of
each character and then sets the characters closer together
than their normal spacing. Many dot-matrix printers have a
feature that causes the printer to reduce the width of each
character and print them closer together, resulting in more
characters fitting on a single line. Compare
expanded.
CONFIG.SYS
n.
A special text file that controls certain aspects of
operating-system behavior in MS-DOS and OS/2. Commands in
the CONFIG.SYS file enable or disable system features, set
limits on resources (for example, the maximum number of open
files), and extend the operating system by loading device
drivers that control hardware specific to an individual
computer system.
configuration
n.
1. In reference to a single microcomputer, the sum of a
system's internal and external components, including memory,
disk drives, keyboard, video, and generally less critical
add-on hardware, such as a mouse, modem, or printer.
Software (the operating system and various device drivers),
the user's choices established through configuration files
such as the AUTOEXEC.BAT and CONFIG.SYS files on IBM PCs and
compatibles, and sometimes hardware (switches and jumpers)
are needed to "configure the configuration" to work
correctly. Although system configuration can be changed, as
by adding more memory or disk capacity, the basic structure
of the system--its architecture--remains the same. See
also AUTOEXEC.BAT, CONFIG.SYS. 2. In relation to
networks, the entire interconnected set of hardware, or the
way in which a network is laid out--the manner in which
elements are connected.
configuration file
n.
A file that contains machine-readable operating
specifications for a piece of hardware or software or that
contains information on another file or on a specific user,
such as the user's logon ID.
connect charge
n.
The amount of money a user must pay for connecting to a
commercial communications system or service. Some services
calculate the connect charge as a flat rate per billing
period. Others charge a varying rate based on the type of
service or the amount of information being accessed. Still
others base their charges on the number of time units used,
the time or distance involved per connection, the bandwidth
of each connected session, or some combination of the
preceding criteria. See also connect time.
n.
A physical link via wire, radio, fiber-optic cable, or other
medium between two or more communications devices.
connectionless
adj.
In communications, of, pertaining to, or characteristic of a
method of data transmission that does not require a direct
connection between two nodes on one or more networks.
Connectionless communication is achieved by passing, or
routing, data packets, each of which contains a source and
destination address, through the nodes until the destination
is reached. See also node (definition 2), packet
(definition 2). Compare connection-oriented.
connection-oriented
adj.
In communications, of, pertaining to, or characteristic of a
method of data transmission that requires a direct
connection between two nodes on one or more networks.
Compare connectionless.
connectivity
n.
1. The nature of the connection between a user's computer
and another computer, such as a server or a host computer on
the Internet or a network. This may describe the quality of
the circuit or telephone line, the degree of freedom from
noise, or the bandwidth of the communications devices. 2.
The ability of hardware devices or software packages to
transmit data between other devices or packages. 3. The
ability of hardware devices, software packages, or a
computer itself to work with network devices or with other
hardware devices, software packages, or a computer over a
network connection.
connectoid
n.
In Windows 95/98 and Windows NT, an icon representing a
dial-up networking connection that also executes a script
for logging onto the network dialed.
connector
n.
1. In hardware, a coupler used to join cables or to join a
cable to a device (for example, an RS-232-C connector used
to join a modem cable to a computer). Most connector types
are available in one of two genders--male or female. A male
connector is characterized by one or more exposed pins; a
female connector is characterized by one or more receptacles
designed to accept the pins on the male connector. See
also DB connector, DIN connector. 2. In programming, a
circular symbol used in a flowchart to indicate a break, as
to another page.
connect time
n.
The amount of time during which a user is actively connected
to a remote computer. On commercial systems, the connect
time is one means of calculating how much money the user
must pay for using the system. See also connect
charge.
console
n.
A control unit, such as a terminal, through which a user
communicates with a computer. In microcomputers, the console
is the cabinet that houses the main components and controls
of the system, sometimes including the screen, the keyboard,
or both. With the MS-DOS operating system, the console is
the primary input (keyboard) and primary output (screen)
device, as evidenced by the device name CON. See also
CON, system console.
consultant
n.
A computer professional who deals with client firms as an
independent contractor rather than as an employee.
Consultants are often engaged to analyze user needs and
develop system specifications.
container
n.
1. In OLE terminology, a file containing linked or embedded
objects. See also OLE. 2. In SGML, an element that
has content as opposed to one consisting solely of the tag
name and attributes. See also element (definition 2),
SGML, tag (definition 3).
content
n.
1. The data that appears between the starting and ending
tags of an element in an SGML or HTML document. The content
of an element may consist of plain text or other elements.
See also element (definition 2), HTML, SGML, tag
(definition 3). 2. The message body of a newsgroup article
or e-mail message.
contention
n.
On a network, competition among stations for the opportunity
to use a communications line or network resource. In one
sense, contention applies to a situation in which two or
more devices attempt to transmit at the same time, thus
causing a collision on the line. In a somewhat different
sense, contention also applies to a free-for-all method of
controlling access to a communications line, in which the
right to transmit is awarded to the station that wins
control of the line. See also CSMA/CD. Compare
token passing.
context-sensitive help
n.
A form of assistance in which a program that provides
on-screen help shows information to the user concerning the
current command or operation being attempted.
context-sensitive menu
n.
A menu that highlights options as available or unavailable
depending on the context in which the option is called. The
menus on Windows' menu bar, for example, are context
sensitive; options such as "copy" are grayed out if nothing
is selected.
context switching
n.
A type of multitasking; the act of turning the central
processor's "attention" from one task to another, rather
than allocating increments of time to each task in turn.
See also multitasking, time slice.
contextual search
n.
A search operation in which the user can direct a program to
search specified files for a particular set of text
characters.
contiguous
adj.
Having a shared boundary; being immediately adjacent. For
example, contiguous sectors on a disk are data-storage
segments physically located next to one another.
contiguous data structure
n.
A data structure, such as an array, that is stored in a
consecutive set of memory locations. See also data
structure. Compare noncontiguous data structure.
continuous carrier
n.
In communications, a carrier signal that remains on
throughout the transmission, whether or not it is carrying
information.
continuous processing
n.
The processing of transactions as they are input to the
system. Compare batch processing (definition 3).
contrast
n.
1. The degree of difference between light and dark extremes
of color on a monitor or on printed output. 2. The control
knob by which the contrast of a monitor is changed.
control
n.
1. Management of a computer and its processing abilities so
as to maintain order as tasks and activities are carried
out. Control applies to measures designed to ensure
error-free actions carried out at the right time and in the
right order relative to other data-handling or
hardware-based activities. In reference to hardware, control
of system operations can reside in a data pathway called a
control bus. In reference to software, control
refers to program instructions that manage data-handling
tasks. 2. In a graphical user interface, an object on the
screen that can be manipulated by the user to perform an
action. The most common controls are buttons, which allow
the user to select options, and scroll bars, which allow the
user to move through a document or position text in a
window.
control bus
n.
The set of lines (conductors) within a computer that carry
control signals between the central processing unit (CPU)
and other devices. For example, a control bus line is used
to indicate whether the CPU is attempting to read from
memory or to write to it; another control bus line is used
by memory to request an interrupt in case of a memory error.
control character
n.
1. Any of the first 32 characters in the ASCII character set
(0 through 31 in decimal representation), each of which is
defined as having a standard control function, such as
carriage return, linefeed, or backspace. 2. Any of the 26
characters Control-A through Control-Z (1 through 26 in
decimal representation) that can be typed at the keyboard by
holding the Control key down and typing the appropriate
letter. The six remaining characters with control functions,
such as Escape (ASCII 27), cannot be typed using the Control
key. Compare control code.
control code
n.
One or more nonprinting characters used by a computer
program to control the actions of a device, used in
printing, communications, and management of display screens.
Control codes are mainly employed by programmers or by users
to control a printer when an application program does not
support the printer or one of its specialized features. In
video, control codes are sent from a computer to a display
unit to manipulate the appearance of text or a cursor on the
screen. Popular video control code sets are ANSI and VT-100.
Also called escape sequence, setup string. See
also control character.
Control key
n.
A key that, when pressed in combination with another key,
gives the other key an alternative meaning. In many
application programs, Control (labeled CTRL or Ctrl on a PC
keyboard) plus another key is used as a command for special
functions. See also control character (definition 2).
controller
n.
A device on which other devices rely for access to a
computer subsystem. A disk controller, for example, controls
access to one or more disk drives, managing physical and
logical access to the drive or drives.
control panel
n.
In Windows and Macintosh systems, a utility that allows the
user to control aspects of the operating system or hardware,
such as system time and date, keyboard characteristics, and
networking parameters.
control unit
n.
A device or circuit that performs an arbitrating or
regulating function. For example, a memory controller chip
controls access to a computer's memory and is the control
unit for that memory.
conventional memory
n.
The amount of RAM addressable by an IBM PC or compatible
machine operating in real mode. This is typically 640
kilobytes (KB). Without the use of special techniques,
conventional memory is the only kind of RAM accessible to
MS-DOS programs. See also protected mode, real mode.
Compare expanded memory, extended memory.
converter
n.
Any device that changes electrical signals or computer data
from one form to another. For example, an analog-to-digital
converter translates analog signals to digital signals.
cookbook1
adj.
Of, pertaining to, or characteristic of a book or manual
that presents information using a step-by-step approach. For
example, a cookbook approach to programming might present a
series of sample programs that the reader could analyze and
adapt to his or her own needs.
cookbook2
n.
A computer book or manual that presents information using a
step-by-step approach. Most often, cookbook refers to
a programming guide, but it can refer to a book that shows
how to accomplish specialized tasks in an application.
cookie
n.
1. A block of data that a server returns to a client in
response to a request from the client. 2. On the World Wide
Web, a block of data that a Web server stores on a client
system. When a user returns to the same Web site, the
browser sends a copy of the cookie back to the server.
Cookies are used to identify users, to instruct the server
to send a customized version of the requested Web page, to
submit account information for the user, and for other
administrative purposes. 3. Originally an allusion to
"fortune cookie," a UNIX program that outputs a different
message, or "fortune," each time it is used. On some
systems, the cookie program is run during user logon.
cookie filtering tool
n.
A utility that prevents a cookie on a Web browser from
relaying information about the user requesting access to a
Web site. See also cookie (definition 2).
cooperative multitasking
n.
A type of multitasking in which one or more background tasks
are given processing time during idle times in the
foreground task only if the foreground task allows it. This
is the primary mode of multitasking in the Macintosh
operating system. See also background1,
context switching, foreground 1, multitasking,
time slice. Compare preemptive multitasking.
cooperative processing
n.
A mode of operation characteristic of distributed systems in
which two or more computers, such as a mainframe and a
microcomputer, can simultaneously carry out portions of the
same program or work on the same data. Compare
distributed processing.
coprocessor
n.
A processor, distinct from the main
microprocessor, that performs additional functions or
assists the main microprocessor. The most common type of
coprocessor is the floating-point coprocessor, also
called a numeric or math coprocessor, which is
designed to perform numeric calculations faster and better
than the general-purpose microprocessors used in personal
computers. See also floating-point processor.
copy
vb.
To duplicate information and reproduce it in another part of
a document, in a different file or memory location, or in a
different medium. A copy operation can affect data ranging
from a single character to large segments of text, a
graphics image, or one to many data files. Text and
graphics, for example, can be copied to another part of a
document, to the computer's memory (by means of a temporary
storage facility such as the Microsoft Windows or Apple
Macintosh Clipboard), or to a different file. Similarly,
files can be copied from one disk or directory to another,
and data can be copied from the screen to a printer or to a
data file. In most cases, a copy procedure leaves the
original information in place. Compare cut and paste,
move.
copy program
n.
1. A program designed to duplicate one or more files to
another disk or directory. 2. A program that disables or
circumvents the copy-protection device on a computer program
so that the software can be copied, often illegally, to
another disk. See also copy protection.
copyright
n.
A method of protecting the rights of an originator of a
creative work, such as a text, a piece of music, a painting,
or a computer program, through law. In many countries the
originator of a work has copyright in the work as soon as it
is fixed in a tangible medium (such as a piece of paper or a
disk file); that rule applies in the United States for works
created after 1977. Registration of a copyright, or the use
of a copyright symbol, is not needed to create the copyright
but does strengthen the originator's legal powers.
Unauthorized copying and distribution of copyrighted
material can lead to severe penalties, whether done for
profit or not. Copyrights affect the computer community in
three ways: the copyright protection of software, the
copyright status of material (such as song lyrics)
distributed over a network such as the Internet, and the
copyright status of original material distributed over a
network (such as a newsgroup post). The latter two involve
electronic media that are arguably not tangible, and
legislation protecting the information disseminated through
electronic media is still evolving. See also fair
use, General Public License.
CORBA
n.
Acronym for Common Object Request Broker Architecture. A
specification developed by the Object Management Group in
1992 in which pieces of programs (objects) communicate with
other objects in other programs, even if the two programs
are written in different programming languages and are
running on different platforms. A program makes its request
for objects through an object request broker, or
ORB, and thus does not need to know the structure of the
program from where the object comes. CORBA is designed to
work in object-oriented environments. See also object
(definition 2), Object Management Group, object-oriented.
core
n.
One of the types of memory built into computers before
random access memory (RAM) was available or affordable. Some
people still use the term to refer to the main memory of any
computer system, as in the phrase core dump--a
listing of the raw contents of main memory at the moment of
a system crash. Compare RAM.
core program
n.
A program or program segment that is resident in random
access memory (RAM).
corruption
n.
A process wherein data in memory or on disk is
unintentionally changed, with its meaning thereby altered or
obliterated.
cost-benefit analysis
n.
The comparison of benefits to costs for a particular item or
action. Cost-benefit analysis is often used in MIS or IS
departments to determine such things as whether purchasing a
new computer system is a good investment or whether hiring
more staff is necessary. See also IS, MIS.
country-specific
adj.
Of, pertaining to, or characteristic of hardware or software
that uses characters or conventions unique to a particular
country or group of countries. Country-specific does
not necessarily refer to spoken languages, although it does
allow for special characters (such as accent marks) that are
language-specific. Generally, the features considered
country-specific include keyboard layout (including
special-character keys), time and date conventions,
financial and monetary symbols, decimal notation (decimal
point or comma), and alphabetic sorting order. Such features
are handled either by a computer's operating system (for
example, by the Keyboard and Country commands in MS-DOS) or
by application programs that offer options for tailoring
documents to a particular set of national or international
conventions.
courseware
n.
Software dedicated to education or training.
CP/M
n.
Acronym for Control Program/Monitor. A line of operating
systems from Digital Research, Inc., for microcomputers
based on Intel microprocessors. The first system, CP/M-80,
was the most popular operating system for 8080- and
Z80-based microcomputers. Digital Research also developed
CP/M-86 for 8086/8088-based computers, CP/M-Z8000 for Zilog
Z8000-based computers, and CP/M-68K for Motorola 68000-based
computers. When the IBM PC and MS-DOS were introduced,
common use of CP/M by end users dwindled. DRI continues to
enhance the CP/M line, supporting multitasking with the
concurrent CP/M and MP/M products. See also MP/M.
CPU
n.
Short for central processing unit.
CPU cache
n.
A section of fast memory linking the central processing unit
(CPU) and main memory that temporarily stores data and
instructions the CPU needs to execute upcoming commands and
programs. Considerably faster than main memory, the CPU
cache contains data that is transferred in blocks, thereby
speeding execution. The system anticipates the data it will
need through algorithms. Also called cache memory,
memory cache. See also cache, central processing
unit, VCACHE.
CPU cycle
n.
1. The smallest unit of time recognized by the central
processing unit (CPU)--typically a few hundred-millionths of
a second. 2. The time required for the CPU to perform the
simplest instruction, such as fetching the contents of a
register or performing a no-operation instruction (NOP).
Also called clock tick.
CPU fan
n.
An electric fan usually placed directly on a central
processing unit (CPU) or on the CPU's heat sink to help
dissipate heat from the chip by circulating air around it.
See also central processing unit, heat sink.
CPU speed
n.
A relative measure of the data-processing capacity of a
particular central processing unit (CPU), usually measured
in megahertz. See also central processing unit.
CPU time
n.
In multiprocessing, the amount of time during which a
particular process has active control of the central
processing unit (CPU). See also central processing
unit, multiprocessing.
cracker
n.
A person who overcomes the security measures of a computer
system and gains unauthorized access. The goal of some
crackers is to obtain information illegally from a computer
system or use computer resources. However, the goal of the
majority is to merely break into the system. See also
hacker.
crash1
n.
The failure of either a program or a disk drive. A program
crash results in the loss of all unsaved data and can leave
the operating system unstable enough to require restarting
the computer. A disk drive crash, sometimes called a disk
crash, leaves the drive inoperable and can cause loss of
data. See also abend, head crash.
crash2
vb.
1. For a system or program, to fail to function correctly,
resulting in the suspension of operation. See also
abend. 2. For a magnetic head, to hit a recording medium,
with possible damage to one or both.
crash recovery
n.
The ability of a computer to resume operation after a
disastrous failure, such as the failure of a hard drive.
Ideally, recovery can occur without any loss of data,
although usually some, if not all, data is lost. See also
crash1.
Cray-1
n.
An early supercomputer developed in 1976 by Seymour Cray.
Extremely powerful in its day, the 64-bit Cray-1 ran at 75
MHz and was capable of executing 160 million floating-point
operations per second. See also supercomputer.
CRC
n.
Acronym for cyclical (or cyclic) redundancy check. A
procedure used in checking for errors in data transmission.
CRC error checking uses a complex calculation to generate a
number based on the data transmitted. The sending device
performs the calculation before transmission and sends its
result to the receiving device. The receiving device repeats
the same calculation after transmission. If both devices
obtain the same result, it is assumed that the transmission
was error-free. The procedure is known as a redundancy check
because each transmission includes not only data but extra
(redundant) error-checking values. Communications protocols
such as XMODEM and Kermit use cyclical redundancy checking.
creator
n.
On the Apple Macintosh, the program that creates a file.
Files are linked to their creators by creator codes; this
link enables the operating system to open the creator
application when a document file is opened.
crop
vb.
In computer graphics, to cut off part of an image, such as
unneeded sections of a graphic or extra white space around
the borders. As in preparing photographs or illustrations
for traditional printing, cropping is used to refine or
clean up a graphic for placement in a document.
crop marks
n.
1. Lines drawn at the edges of pages to mark where the paper
will be cut to form pages in the final document. See also
registration marks. 2. Lines drawn on photographs or
illustrations to indicate where they will be cropped, or
cut. See also crop.
cross-hatching
n.
Shading made up of regularly spaced, intersecting lines.
Cross-hatching is one of several methods for filling in
areas of a graphic.
cross-linked files
n.
In Windows 95, Windows 3.x, and MS-DOS, a file-storage error
occurring when one or more sections, or clusters, of
the hard drive or a floppy disk have been erroneously
allocated to more than one file in the file allocation
table. Like lost clusters, cross-linked files can result
from the ungraceful exit (messy or abrupt termination) of an
application program. See also file allocation table,
lost cluster.
cross-platform
adj.
Of, pertaining to, or characteristic of a software
application or hardware device that can be run or operated
on more than one system platform.
cross-post
vb.
To copy a message or news article from one newsgroup,
conference topic, e-mail system, or other communications
channel to another--for example, from a Usenet newsgroup to
a CompuServe forum or from e-mail to a newsgroup.
crosstalk
n.
Interference caused by a signal transferring from one
circuit to another, as on a telephone line.
CRT
n.
Acronym for cathode-ray tube. The basis of the television
screen and the standard microcomputer display screen. A CRT
display is built around a vacuum tube containing one or more
electron guns whose electron beams rapidly sweep
horizontally across the inside of the front surface of the
tube, which is coated with a material that glows when
irradiated. Each electron beam moves from left to right, top
to bottom, one horizontal scan line at a time. To keep the
screen image from flickering, the electron beam refreshes
the screen 30 times or more per second. The clarity of the
image is determined by the number of pixels on the screen.
See also pixel, raster, resolution (definition 1).
CRT controller
n.
The part of a video adapter board that generates the video
signal, including the horizontal and vertical
synchronization signals. See also video adapter.
cryptoanalysis
n.
The decoding of electronically encrypted information for the
purpose of understanding encryption techniques. See also
cryptography, encryption.
cryptography
n.
The use of codes to convert data so that only a specific
recipient will be able to read it, using a key. The
persistent problem of cryptography is that the key must be
transmitted to the intended recipient and may be
intercepted. Public key cryptography is a recent significant
advance. See also code1 (definition 2),
encryption, PGP, private key, public key.
C shell
n.
One of the command line interfaces available under UNIX. The
C shell is very usable but is not on every system.
Compare Bourne shell, Korn shell.
CSMA/CD
n.
Acronym for Carrier Sense Multiple Access with Collision
Detection. A network protocol for handling situations in
which two or more nodes (stations) transmit at the same
time, thus causing a collision. With CSMA/CD, each node on
the network monitors the line and transmits when it senses
that the line is not busy. If a collision occurs because
another node is using the same opportunity to transmit, both
nodes stop transmitting. To avoid another collision, both
then wait for differing random amounts of time before
attempting to transmit again. Compare token passing.
CTL
n.
Short for control. See control character (definition
2), Control key.
CTRL
or Ctrl Short for control. A
designation used to label the Control key on computer
keyboards. See also control character (definition 2),
Control key.
Ctrl-Alt-Del
n.
A three-key combination used with IBM and compatible
computers to restart (reboot) the machine. Pressing
Ctrl-Alt-Del (Control-Alt-Delete) causes a warm boot in
MS-DOS--the computer restarts but does not go through all of
the internal checks involved when power to the system is
switched on (cold boot). In Windows 95 and Windows NT,
Ctrl-Alt-Del provides a dialog box from which the user may
choose to shut down the computer or end any current tasks.
Ctrl-C
n.
1. In UNIX, the key combination used to break out of a
running process. 2. The keyboard shortcut recognized by many
programs (as in Windows) as an instruction to copy the
currently selected item.
Ctrl-S
n.
1. On systems in which a software handshake is used between
terminals and a central computer, the key combination used
to suspend output. Ctrl-Q will resume output after a Ctrl-S
suspension. See also software handshake, XON/XOFF. 2.
A keyboard shortcut recognized by many programs as an
instruction to save the current document or file.
curly quotes
n.
See smart quotes.
current
n.
The flow of electric charge through a conductor, or the
amount of such flow. Current is measured in amperes. See
also ampere, coulomb. Compare volt.
current directory
n.
The disk directory at the end of the active directory
path--the directory that is searched first for a requested
file, and the one in which a new file is stored unless
another directory is specified. See also path
(definition 2).
cursor
n.
1. A special on-screen indicator, such as a blinking
underline or rectangle, that marks the place at which a
keystroke will appear when typed. 2. In reference to
digitizing tablets, the stylus (pointer or "pen"). 3. In
applications and operating systems that use a mouse, the
arrow or other on-screen icon that moves with movements of
the mouse.
cursor blink speed
n.
The rate at which a cursor on screen flashes on and off.
See also cursor (definition 1).
CUSeeMe
n.
A videoconferencing program developed at Cornell University.
It was the first program to give Windows and Mac OS users
the ability to engage in real-time videoconferencing over
the Internet, but it requires a lot of bandwidth (at least
128 Kbps speed) to function properly.
customize
vb.
To modify or assemble hardware or software to suit the needs
or preferences of the user. Traditionally, hardware
customizing ranges from designing an electronic circuit for
a particular customer to putting together a computer
facility tailored to a customer's special need. Software
customizing usually means modifying or designing software
for a specific customer.
custom software
n.
Any type of program developed for a particular client or to
address a special need. Certain products, such as dBASE and
Lotus 1-2-3, are designed to provide the flexibility and
tools required for producing tailor-made applications.
See also CASE.
cut
vb.
To remove part of a document, usually placing it temporarily
in memory so that the cut portion can be inserted (pasted)
elsewhere. Compare delete.
cut and paste
n.
A procedure in which the computer acts as an electronic
combination of scissors and glue for reorganizing a document
or for compiling a document from different sources. In cut
and paste, the portion of a document to be moved is
selected, removed to storage in memory or on disk, and then
reinserted into the same or a different document.
cybercafe
or cyber café n. 1. A
coffee shop or restaurant that offers access to PCs or other
terminals that are connected to the Internet, usually for a
per-hour or per-minute fee. Users are encouraged to buy
beverages or food to drink or eat while accessing the
Internet. 2. A virtual café on the Internet, generally used
for social purposes. Users interact with each other by means
of a chat program or by posting messages to one another
through a bulletin board system, such as in a newsgroup or
on a Web site.
cybercop
n.
A person who investigates criminal acts committed online,
especially fraud and harassment.
Cyberdog
n.
Apple's Internet suite for HTML browsing and e-mail, based
on OpenDoc for easy integration with other applications.
See also OpenDoc.
cybernaut
n.
One who spends copious time online, exploring the Internet.
Also called Internaut. See also cyberspace.
cybernetics
n.
The study of control systems, such as the nervous system, in
living organisms and the development of equivalent systems
in electronic and mechanical devices. Cybernetics compares
similarities and differences between living and nonliving
systems (whether those systems comprise individuals, groups,
or societies) and is based on theories of communication and
control that can be applied to either or both. See also
bionics.
cyberpunk
n.
1. A genre of near-future science fiction in which conflict
and action take place in virtual-reality environments
maintained on global computer networks in a worldwide
culture of dystopian alienation. The prototypical cyberpunk
novel is William Gibson's Neuromancer (1982). 2. A
category of popular culture that resembles the ethos of
cyberpunk fiction. 3. A person or fictional character who
resembles the heroes of cyberpunk fiction.
cybersex
n.
Communication via electronic means, such as e-mail, chat, or
newsgroups, for the purpose of sexual stimulation or
gratification. See also chat1 (definition
1), newsgroup.
cyberspace
n.
1. The advanced shared virtual-reality network imagined by
William Gibson in his novel Neuromancer (1982). 2.
The universe of environments, such as the Internet, in which
persons interact by means of connected computers. A defining
characteristic of cyberspace is that communication is
independent of physical distance.
cybrarian
n.
Software used at some libraries that allows one to query a
database through the use of an interactive search engine.
cycle power
vb.
To turn the power to a machine off and back on in order to
clear something out of memory or to reboot after a hung or
crashed state.
cycle time
n.
The amount of time between a random access memory (RAM)
access and the earliest time a new access can occur. See
also access time (definition 1). |
