📄 apa.htm
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<P><B>Bus topology  </B>A LAN topology that features a linear backbone
on to which nodes are connected. <I>See also</I> tree topology, ring topology, and
star topology.
<H2><A NAME="Heading4"></A><FONT COLOR="#000077">C</FONT></H2>
<P><B>CAD  </B>Computer aided design. Design and engineering processes
aided by the use of computers. In most cases, CAD contributes to the initial design
and test phases through the use of sophisticated design and modeling packages normally
run engineering workstations.</P>
<P><B>CAM  </B>Computer aided manufacturing. Manufacturing processes aided
by computers. With respect to manufacturing, CAM contributes in the area of process
control and quality assurance.</P>
<P><B>CASE  </B>Computer aided software engineering. An approach to the
development of application programming that uses other programs to help generate
parts of (or all of) the final product. At a minimum, CASE might be thought of as
a programming tool.</P>
<P><B>CBEMA  </B>Computer and Business Equipment Manufacturers Association.
An association of U.S. manufacturers that, among other things, sponsors the X.3 standards
committee of ANSI. <I>See also</I> ANSI and X.3.</P>
<P><B>CBX  </B>Computerized branch exchange. A telephone routing exchange
driven by an intelligent device (in other words, a computer).</P>
<P><B>CCIR  </B>Consultative Committee for International Radio. An international
standards body that sets the rules and requirements for radio communications. CCIR
is a committee within the International Telecommunications Union (ITU). <I>See also</I>
ITU and CCITT.</P>
<P><B>CCITT  </B>Consultative Committee for International Telegraphy and
Telephony. An international standards body which sets the rules and requirements
for international communications. CCITT is a committee within the larger International
Telecommunications Union (ITU) and is best known for the development of the X.25
standard for public data networks. <I>See also</I> CCIR and ITU.</P>
<P><B>CCN  </B>Cluster controller node. <I>See</I> cluster controller.</P>
<P><B>CD  </B>Carrier Detect. A lead in the RS-232C interface that signals
that information is being received over the data link. CD is also sometimes called
Data Carrier Detect (DCD). In the full 25-pin RS-232C standard, CD is pin 8. In the
abbreviated 9-pin PC interface, CD is pin 1. <I>See also</I> CTS, RS-232C and RTS.</P>
<P><B>CDE  </B>Common Desktop Environment. Part of the COSE agreement between
major UNIX vendors to present a common interface to all UNIX implementations.</P>
<P><B>CGM  </B>Computer Graphics Metafile. A device-independent format
for the presentation of graphics. Defined as ISO standard 8632.</P>
<P><B>CI  </B>Computer Interconnect. A high-speed, fault-tolerant connection
between DEC VAX systems and a Star Coupler in VAXclusters. <I>See also</I> Star Coupler
and VAXclusters.</P>
<P><B>CICS  </B>Customer Information Control System. An IBM transaction-oriented,
database/data communications system for mainframes.</P>
<P><B>CIM  </B>Computer integrated manufacturing. A total solution to the
computerization of manu-facturing operations that integrates as many related functions
as possible (for example, administration, engineering, purchasing, and manufacturing).</P>
<P><B>CISC  </B>Complex (or complete) instruction set computer. The traditional
architecture for computers in which useful software functions are supported by hardware.
<I>See also</I> RISC.</P>
<P><B>CIXCD  </B>DEC's improved version of its basic CI link between VAX
systems and Star Couplers in VAXclusters. The CIXCD is used with the VAX 9000 systems.</P>
<P><B>Classic  </B>HP applied the term Classic to its HP 3000 CISC models
after it released its HP 3000 RISC models.</P>
<P><B>Cluster controller  </B>A device used to control the interface to
multiple workstations. Cluster controllers are commonly used in remote locations
to interface multiple workstations with a single data communications line. IBM cluster
controllers (often referred to as CCNs) include the 3274 and 5294. Under SNA, a cluster
controller is a PU 2 device.</P>
<P><B>CMIP  </B>Central Management Information Protocol. An OSI standard
for the low-level functions required to perform network management. <I>See also</I>
CMIS.</P>
<P><B>CMIS  </B>Central Management Information Service. An OSI standard
for the high-level functions required to perform network management. <I>See also</I>
CMIP.</P>
<P><B>CMS  </B>Conversational Monitor System. In an IBM mainframe environment,
CMS is the interface between the user and the central Control Program (CP) of the
VM operating system. Multiple copies of CMS are used to support multiple users (but
still only one CP). <I>See also</I> CP.</P>
<P><B>coaxial  </B>In general, a cabling system that uses a central conducting
core that is surrounded by an insulating medium that is, in turn, surrounded by a
protective sheathing. Coaxial cable is used by IBM to connect its 3270 family of
workstations. <I>See also</I> twinaxial.</P>
<P><B>COMMAND.COM  </B>A program supplied with MS-DOS and PC-DOS that performs
the built-in DOS commands. For example, DIR and TYPE are internal commands, while
FORMAT and COPY are external commands. All internal commands are contained within
COMMAND.COM.</P>
<P><B>common communications support  </B>One of three SAA interfaces. The
common communications support interface defines the data formats and protocols that
can be used in an SAA environment. This includes, for example, the SNA 3270 data
format, DIA/DCA and SNADS. <I>See also</I> common programming interface, common user
interface, DCA, DIA, SAA, and SNADS.</P>
<P><B>common programming interface  </B>One of three SAA interfaces. The
common programming interface defines a set of routines for accessing files, programs
and communications devices under SAA. <I>See also</I> common communications support,
common user interface, and SAA.</P>
<P><B>common user interface  </B>One of three SAA interfaces. The common
user interface defines the characteristics of text and graphics screens generated
by SAA-compliant programs and how the user interacts with those displays. <I>See
also</I> common communications support, common programming interface, and SAA.</P>
<P><B>communications controller  </B>In an IBM mainframe environment, a
communications controller is channel-attached to the host and serves to control the
data communication network. IBM communication controllers (often referred to as either
CUCNs or FEPs) include the 3705, 3725, and 3745. Under SNA, a communications controller
is a PU 4 device. <I>See also</I> FEP and ICA.</P>
<P><B>compound document  </B>A document that can include text, graphics,
video and voice data.</P>
<P><B>conditioning  </B>A process applied to<B> </B>standard analog phone
lines to provide filtering in support of less error-prone data transmission. Various
levels of conditioning are available at various costs and are implemented through
specialized equipment.</P>
<P><B>connectionless  </B>A type of networking service in which the sending
side requires no direct or indirect access to the receiving side(s).</P>
<P><B>connection-oriented  </B>A type of networking service in which the
sending and receiving sides are in direct or indirect contact with one another.</P>
<P><B>CORBA  </B>Common Object Request Broker Architecture. A specification
for the development of ORBs. CORBA establishes an environment for software objects
to communicate with each other.</P>
<P><B>CP  </B>Control Program. In an IBM mainframe environment, CP is the
central management facility under the VM operating system.</P>
<P><B>CPF  </B>Control Program Facility. An IBM operating system used on
the System/38 computers.</P>
<P><B>CP/M  </B>An operating system for microcomputers created by Digital
Research. CP/M was king of the hill among microcomputer operating systems prior to
IBM's adoption of MS-DOS (PC-DOS).</P>
<P><B>cps  </B>Characters per second. A measurement of data communications
speed and throughput.</P>
<P><B>CPU  </B>Central processing unit. The core processing unit of a computer
system, in most cases contained in a single chip.</P>
<P><B>CRC  </B>Cyclic Redundancy Check. An error detection scheme in which
the block check character (BCC) is derived from dividing all the serialized bits
in a block by a predetermined binary number. <I>See also</I> BCC and LRC.</P>
<P><B>CSMA/CD  </B>Carrier Sense Multiple Access with Collision Detection.
The LAN discipline (protocol) used by both Ethernet and the IEEE 802.3 standard.
Under CSMA/CD, a device that wishes to transmit on the network first listens for
other activity. If the network is quiet, the device then attempts to transmit. Data
collisions are detected and result in both transmitters retrying their transmissions
after a random amount of time.</P>
<P><B>CSU  </B>Channel service unit. The interface to a Digital Data Service
line. The CSU takes data off the DDS line and feeds it to a Data Service Unit (DSU)
that, in turn, interfaces with the terminal or computer equipment. In many cases,
a CSU is combined with a DSU, into a single unit called an integrated service unit
(ISU). <I>See also</I> DDS, DSU, and ISU.</P>
<P><B>CTERM  </B>A DECnet protocol used by one DEC host to forward information
from a terminal to another host. This is the protocol used by the standard DECnet
SET HOST command.</P>
<P><B>CTOS  </B>An operating system produced by Convergent Technology (Unisys)
for its line of microcomputers. CTOS is a multitasking, multiuser operating system
that is similar in structure to UNIX.</P>
<P><B>CTS  </B>Clear to Send. A lead in the RS-232C interface. CTS is raised
in response to receipt of the Request to Send (RTS) signal. In brief, when one side
of the link wishes to transmit, it raises the RTS line. If the other side is ready
to receive, it responds by raising the CTS line. Once transmission has begun, the
Carrier Detect (CD) line is also raised. In the full 25-pin RS-232C standard, CTS
is pin 5. In the abbreviated 9-pin PC interface, CTS is pin 8. <I>See also</I> CD,
RS-232C, and RTS.</P>
<P><B>CTS-300  </B>DEC's commercial operating system for the PDP-11 family
of computers. <I>See also</I> DSM-11, RSTS, and RSX.</P>
<P><B>CUCN  </B>Communications controller node. <I>See</I> communications
controller.</P>
<P><B>CUT  </B>Control unit terminal. Another term used by IBM for its
general-purpose workstations.
<H2><A NAME="Heading5"></A><FONT COLOR="#000077">D</FONT></H2>
<P><B>DAP  </B>Data Access Protocol. A low-level DECnet protocol responsible
for the movement of information from system to system.</P>
<P><B>DARPA  </B>Defense Advanced Research Project Agency, formerly known
as ARPA. An agency within the U.S. Department of Defense that was instrumental in
the development of TCP/IP. The agency's ARPANET network was the precursor of the
modern Internet. <I>See also</I> TCP/IP.</P>
<P><B>DASD  </B>Direct access storage device. An IBM term that refers to
IBM mass storage devices (disk drives).</P>
<P><B>Data Link Layer  </B>The second (from the bottom) layer of the OSI
Reference Model. The Data Link layer defines the protocols used to move data across
the Physical Layer (for example, HDLC, LAP-B or IEEE 802.2). The Data Link Layer
is sometimes also called the Logical Link Layer. <I>See also</I> OSI Reference Model.</P>
<P><B>DB2  </B>IBM's relational database for mainframes running the MVS
or VM operating systems.</P>
<P><B>DCA  </B>Document Content Architecture. An IBM document specification
that defines the structure and contents of documents in both revisable and final
forms. Under DCA, revisable documents include their editing history, while final
form documents are the net result of all edits.</P>
<P><B>DCD  </B>Data Carrier Detect. <I>See</I> CD.</P>
<P><B>DCE  </B>Data communications equipment. A device such as a modem
that facilitates a data communications link. The DCE interfaces with the data terminal
equipment (DTE), which is the origin or destination of the information. A complete
link includes a DTE interfacing with a DCE that interfaces with another DCE that,
in turn, interfaces with another DTE. In direct connection environments, one side
of the connection (normally the computer) emulates a DCE interface. <I>See also</I>
DTE.</P>
<P><B>DDCMP  </B>Digital Data Communications Message Protocol. A DECnet
byte-oriented protocol that ensures the integrity and correct sequencing of messages
between adjacent nodes. DDCMP can be used for synchronous or asynchronous transmissions
and is most frequently used to implement DECnet wide-area connections over conventional
leased lines.</P>
<P><B>DDM  </B>Distributed Data Management. An IBM product geared for its
mid-range machines. DDM enables a system to access remote files over a network at
both the record and the file level. <I>See also</I> DIA and SNADS.</P>
<P><B>DDN  </B>Defense Data Network. The multivendor WAN used by the U.S.
Department of Defense.</P>
<P><B>DDS  </B>Digital Data Service. A leased line using digital transmission
that can provide data communications rates up to 56 Kbps. When DDS is employed, the
modems used with analog lines are replaced by a Channel Service Unit (CSU) and a
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