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Modernz 20a
C
=
A high-level programming language for writing systems software. The
UNIX operating system was written using the C language. C language
reduces source code length, which could possibly reduce object code
size.
C-48
====
The contiguous 48 states of the United States; excludes Alaska and
Hawaii. Also called CONUS.
cable
=====
A number of electrical or optical conductors assembled and covered
with a sheath.
Call Request (CRQ)
==================
An X.25 packet requesting to set up a call and containing the calling
and called DTE addresses (in addition to other various X.25 fields).
called address
==============
An address (usually X.121) in packed binary-coded decimal digits
(maximum 15) specifying the requested destination of a call.
calling address
===============
An address (usually X.121) in packed binary-coded decimal digits
(maximum 15) specifying the original requestor of a call.
carrier
=======
An analog signal (at a fixed amplitude and frequency) combined with
an information signal in a modulation process producing a signal for
transmission. A carrier provides sufficient power so that a signal
can be reliably detected at some other point or points. Modulation
makes a more powerful signal. The term carrier may refer to this
powerful signal either before or (more commonly) after modulation.
Also called carrier wave or carrier frequency.
Carrier Detect (CD)
===================
The state of an EIA signal in a modem that is true when the modem
has detected a carrier signal on its receive channel.
Carrier Present (CP)
====================
An RS-232-C interface signal.
Carrier Sense Multiple Access/Collection Detection (CSMA/CD)
============================================================
A method for handling network access of several stations on a Local
Area Network (LAN). Collision Detection (CD) is a refinement of this
method whereby a station on a LAN detects and compensates for the
undesirable collisions that could mix data when several stations try
to transmit simultaneously.
CBEMA
=====
Computer and Business Manufacturers Association.
CBX
===
Computerized Branch and Exchange.
CCIR
====
International Radio Consultive Committee.
CCITT
=====
Comite Consultatif International de Telephonie et de Telegraphie or
International Telegraph and Telephone Consultative Committee. An
organization of the United Nations, whose task it is to make technical
recommendations about telephone, telegraph, and data communications
interfaces.
CCSA
====
Common Control Switching Arrangement. A dedicated, switched network
leased by a user to handle communication requirements among various
locations.
CCT
===
Circuit Characteristic Type. A number that indicates a circuit's
throughput class, batch or interactive circuit type, and protocol.
For example, CCT 0 identifies the circuit as an auxiliary circuit.
CCU
===
Cluster Control Unit. A device that can control all communications
between a number of terminals or other devices and a host computer.
In a TYMNET network, the Cluster Controller is connected to terminal
interface (TIF) software that communicates across the network to a
host interface (HIF).
CD
==
Carrier Detect. The state of an EIA signal in a modem that is true
when the modem has detected a carrier signal on its receive channel.
CEI
===
Current Empty Index.
CEN
===
Comite Europeen de Normalisation.
CENELEC
=======
Comite Europeen de Normalisation Electrotechnique.
centralized network
===================
A time-sharing system in which channels radiate from a central
computer system.
CEPT
====
European Conference of Postal and Telecommunication Administration.
channel
=======
A means of transmittin' information from one point to another point.
A space allocated to a user on a link; a means of oneway transmission.
Usually implies a specific set of physical resources, especially a
range of frequencies on some transmission medium. The transmission
medium can be open (radio), or closed (pairs of telephone company
wire, coaxial cable, or other types of wiring and cabling).
character
=========
A basic unit of information defined by a standard alphabet: upper and
lowercase symbols, numerals, punctuation marks, special symbols, and
nonprinted characters such as spaces and carriage returns, which are
used for control purposes.
Character Mode Translator (CMT)
===============================
A BT North America network-resident protocol conversion software
program that allows ASCII character mode terminals to access non-ASCII
character mode hosts. Program examples are as follows:
CMTI (I refers to IBM) translates ASCII data stream to
EBCDIC 3270 data stream.
CMTK (K refers to Katakana or Kanji) translates ASCII to
Katakana or Kanji.
CMTU (U refers to Universal Terminal Systems [UTS])
translates ASCII to UTS applications.
Character Mode Translator Operations Manager (COM)
==================================================
A subprocess of the CMT slot. COM allows the user to monitor and
control certain aspects of the CMT slot. It can be accessed with a
standard login.
character pair
==============
Two continuous bytes of memory.
chassis
=======
The mechanical structure in the Engine and Turbo Engine cabinets, which
house the logic and protocol interface boards.
checking
========
A method of verifying the accuracy of data transmitted by using
polynomial functions of the data transmitted against the data
received. Also called Cyclic Redundancy Check (CRC).
checking-echo
=============
A method of checking the accuracy of data transmission. The receiver
returns the data to the sender for comparison with the original data.
Also called loop checking.
checkpoint
==========
An address in a program that is recorded in the event log.
checksum
========
The last 4 bytes of a packet, which are used to check the validity of
data. Also used to refer to numbers or strings that confirm the
validity of a file.
checksum error
==============
An error condition on a line, which is detected when a node receives a
packet whose checksum fields do not match the checksums calculated for
the received packet. When this condition is detected, the packet is
discarded or the message BAD ACK or BAD RECN is sent.
circuit
=======
A complete electrical path. A data path from host-to-host or
host-to-terminal. A collection of buffer pairs and channels connecting
two ports.
circuit board
=============
A board to which electronic components such as transistors, resistors,
and microprocessors are affixed. Also called printed circuit board or
card.
Circuit Characteristic Type (CCT)
=================================
A number that indicates a circuit's throughput class, batch or
interactive circuit type, and protocol. For example, CCT 0 identifies
the circuit as an auxiliary circuit.
circuit label
=============
The ISIS relative port number assigned by the MUX, or the
alphanumeric designation of a circuit assigned by the user.
Circuit Multiplexer (MUX)
=========================
An ISIS slot program that allows users to build and maintain
multiple circuits to other tools and applications on their hosts.
A MUX also allows its users to communicate with other users with a
Talk mode facility. A MUX is accessed over a Boss circuit as a host
in an ISIS slot.
circuit segment
===============
That portion of a circuit existing in a single node.
circuit switching
=================
A method of communication that establishes an end-to-end connection
between two points on a communication network for the life of the
session only. The physical route of the circuit can vary from one
session to the next or can be different for each session.
CIS
===
Configuration Information System.
class
=====
A set of hosts or nodes that is part of an origination list used to
control access to the network. This list can be used as an exclusive
list (barring access) or an inclusive list (allowing access) from these
nodes or hosts to the network.
Class and Group tables
======================
A database on each Supervisor's disk that contains lists of origination
hosts and nodes and destination hosts in a TYMNET network. At login,
the Supervisor reads from this database to validate the user's circuit
request. The NETVAL program manages this database and forwards this
information to each Supervisor.
Clear To Send (CTS)
===================
A signal sent by the DCE to the DTE notifying the DTE that it can begin
to transmit data. Contrast with Request To Send (RTS).
client
======
A software program that requests a service. The client is paired with
the server; the client is the requestor, the server the provider.
See server.
clock
=====
A device that generates periodic signals used for synchronization.
Closed User Group (CUG)
=======================
A group that can only receive data from or transmit data to other
users within the same group.
Cluster Controller (CC) or Cluster Control Unit (CCU)
=====================================================
A device that can control all communications between a number of
terminals or other devices and a host computer. In a TYMNET network,
the Cluster Controller is connected to terminal interface (TIF)
software that communicates across the network to a host interface
(HIF).
Cluster Remote Display Unit (CRDU)
==================================
A terminal interface (TIF) that replaces a cluster control unit (CCU)
and hardware-dominated loop-line network. Customized service for
special application configurations.
CMF
===
Code Management Facility. A node configuration and code generation
system that runs as an application program under the UNIX operating
system.
CMOS
====
Complementary Metal Oxide Semiconductor.
CMT
===
Character Mode Translator. A BT North America network-resident
protocol conversion (CMT) software program that allows ASCII character
mode terminals to access non-ASCII character mode hosts.
Program examples are as follows:
CMTI (I refers to IBM) translates ASCII data stream to
EBCDIC 3270 data stream.
CMTK (K refers to Katakana or Kanji) translates ASCII to
Katakana or Kanji.
CMTU (U refers to Universal Terminal Systems [UTS])
translates ASCII to UTS applications.
coaxial cable
=============
Cable that consists of a central metal conductor surrounded by a
dielectric material that is in turn wrapped by a second conductor,
all of which is encased in an insulating sheath. Also called coax.
COBOL
=====
Common Business-Oriented Language. A high-level language developed
for business data-processing applications.
code
====
A group of characters that has a particular meaning. Also, a general
term used to refer to the text of computer programs or portions of
programs. A system of symbols representing data or instructions in a
computer.
BT North America source codes are currently written in the
following languages: assembly, C, andCPASCAL.
BT North America codes currently written in assembly are
CONSAT, Node Code, PROBE, SNA, TYMCOM, and X.25.
BT North America codes currently written in C are ISOM-68K
and Turbo-SCP.
BT North America codes currently written in CPASCAL are
OnTyme, NETVAL, RAM, and TMCS.
Code Management Facility (CMF)
==============================
A node configuration and code generation system that runs as an
application program under the UNIX operating system.
Coder/Decoder (CODEC)
=====================
An electronic device used in digital telephone systems to convert
analog signals to digital signals or vice versa.
COM
===
Character Mode Translator Operations Manager. A subprocess of the CMT
slot. COM allows the user to monitor and control certain aspects of
the CMT slot. It can be accessed with a standard login.
command
=======
A request for an operation to be performed. Any input to a computer or
a program that causes it to take some specified action.
command circuit
===============
A virtual circuit that connects a node to the active Supervisor.
Network management messages are transmitted via a command circuit from
the Supervisor to the node's Node Code. A command circuit must exist
for the node to be in the TYMNET network.
command file
============
A system generation file containing a series of commands used to
create a NIB file.
Common Business-Oriented Language (COBOL)
=========================================
A high-level language developed for business data-processing
applications.
common carrier
==============
A legal entity required by law to carry goods or information of any
qualified customer at publicly established and regulated rates. An
example is AT&T. TYMNET is not a common carrier.
Common Control Switching Arrangement (CCSA)
===========================================
A dedicated, switched network leased by a user to handle communication
requirements among various locations.
communications controller
=========================
Another term for front-end processor.
Compact XL
==========
An intermediate-sized node in the Engine family of communications
processors. Supports applications requiring a moderate number of
interconnections. Provides synchronous and asynchronous communications
between dissimilar devices and uses CPU III, MAC III and SIO II boards,
with up to five optional I/O cards and a 160-MB hard disk.
compatibility
=============
The ability of two types of equipment or software using the same
protocols to communicate.
compiler
========
A computer program that converts source code (programming language)
into object code (machine-readable language). See also assembler.
complementary buffer
====================
One buffer of a buffer pair, which holds data traveling in the opposite
direction on a circuit.
compound passthrough circuit
============================
A circuit passing through a Multi-Node Code (MNC) system that enters a
node on one Node Code slot and exits on a different Node Code slot.
The Turbo Engine uses MNC. Contrast with simple passthrough circuit.
computer
========
Any machine that can accept data in a certain form, process the data
by problem-solving (perform a mathematical or logical operation on the
data) and supply the results of the operation. Also, any machine that
can control a process.
concentrator
============
A device that multiplexes several low-speed communications lines onto a
single high-speed trunk.
Concurrent Pascal
=================
A version of the high-level PASCAL language, which is structured
logically for both synchronous and asynchronous multiple process
applications.
Concurrent Pascal Compiler (CPASCAL)
====================================
A software program that translates source code written in Concurrent
Pascal (CPASCAL) programming language, into object code. This program,
which is formatted for Engine loading, produces a code that can run
several processes at the same time. See code.
conditioning
============
A type of electrical balancing that provides improved electrical
characteristics for high-speed data transmissions over a leased-line
circuit. For example, equalizing the attenuation distortion between
the higher and lower frequencies adjusts the slightly degraded waveform
enough for it to become acceptable.
configuration
=============
A functional arrangement of hardware and software that performs
specific node functions.
Configuration file
==================
A system generation parameter file containing statements that
customize slot code.
Configurator
============
A planning and analysis tool used to design or reconfigure a TYMNET
network. This tool can develop designs based on network performance
and point-to-point traffic requirements, designing a network of up to
200 nodes and 4,000 links, and can specify node and neighbor node
association. See TYMNET On-line Planning System (TOPS).
connect time
============
A measure of system usage by a given user. Also, the length of time it
takes a switching system to connect the calling party to the called
party.
Consolidated TYMSAT (CONSAT)
============================
An asynchronous terminal interface (TIF) code. TYMNET network-resident
software that makes it possible for the network to communicate with
terminals or personal computers that use asynchronous protocol.
constant ratio
==============
A code in which the ratio of ones to zeros in each character is
constant. See IBM 4 of 8.
context switcher
================
A portion of TYM2 Solo Node Code that regulates the execution of
independent processes in a node.
control code
============
A data item that performs signaling functions between software
packages. Usually one byte. Common ASCII control codes are
NUL ENQ LF SI DC4 EM RS
SOH ACK VT DLE NAK SUB US
STX BEL FF DC1 SYN ESC
ETX BS CR DC2 ETB FS
EOT HT SO DC3 CAN GS
Control Table Area (CTA)
========================
A memory segment (segment E) that contains descriptors of a slot's
running configuration, such as, which segments are in use, the host
numbers assigned to that slot, and the number of ports available to
each host in that slot. See slot. See also segment.
controller
==========
A device that automatically regulates a controlled variable or system.
Controlling User Directory (CUD)
================================
A collection of all user validation data (username, password, and
network access). Accessed by NETVAL, the CUD is periodically copied
to the Master User Directory (MUD) of each Supervisor in the network.
CONUS
=====
Continental United States; excludes Alaska and Hawaii.
conversion boundary
===================
A type of interface program that translates one protocol into another
protocol.
Coordinated Universal Time (UTC)
================================
The mean solar time for the meridian at Greenwich, England, used as a
basis for calculating time throughout most of the world. Formerly
called Greenwich Mean Time (GMT). GMT became Coordinated Universal
Time (UTC) when the atomic clock was moved to Paris, France. In some
TYMNET programs, UTC is stored as a 64-bit binary number that
represents the time elapsed since January 1, 1974.
coprocessor
===========
A secondary processor that performs specialized data-processing tasks.
core memory
===========
An older, slower, and bulkier type of magnetic main memory. The term
is often used as a synonym for other types of memory. Its one advantage
is that it is nonvolatile when the power is shut off.
COS
===
Corporation for Open Systems.
CP
==
Carrier Present. An RS-232-C interface signal.
CPASCAL
=======
Concurrent Pascal Compiler. A software program that translates source
code written in Concurrent Pascal (CPASCAL) programming language into
object code. This program, which is formatted for Engine loading,
produces a code that can run several processes at the same time.
See PASCAL.
CPE
===
Customer Premise Equipment. Equipment located at a customer site;
the equipment might not be owned by the customer.
cps
===
Characters per second or cycles per second.
CPU I
=====
Central Processing Unit I. A BT North America controller board in the
Engine family of communication processors that performs all arithmetic
and logical operations. The CPU I is directly cabled to the ROM and
I/O board.
CPU III
=======
Central Processing Unit III. A BT North America controller board in the
Engine family of communication processors that performs all arithmetic
and logical operations. The CPU III combines the features of the CPU I
and the ROM and I/O boards.
crash
=====
The halting of an execution of computer code, a portion of computer
code, or the whole machine due to hardware failure, endless loop,
or block.
crash options
=============
A set of parameters that determines what actions a slot can take
following a crash.
crash register
==============
A description of the contents of registers as they were at the time
of a crash.
crash table
===========
An area of memory that records the slot's crash history.
CRC
===
Cyclic Redundancy Check. An error-detection technique used to check the
accuracy of frames transmitted over a data link. A mathematical
calculation performed by Node Code to ensure data integrity of the
packets transmitted between nodes.
CRDU
====
Cluster Remote Display Unit. A terminal interface (TIF) that replaces
a cluster control unit (CCU) and hardware-dominated loop-line network.
Customized service for special application configurations.
crossover cable
===============
A cable or double connection that can mate similar cables or equipment.
For example, the transmit data signal on the originating end becomes
the receiving data signal on the terminating end. Also called a
null-modem cable.
CRQ
===
Call Request. An X.25 packet requesting to set up a call and containing
the calling and called DTE addresses (in addition to other various X.25
fields).
CRT
===
Cathode Ray Tube.
crypto messages
===============
Diagnostic messages that are continuously generated by Node Code. The
most recent crypto messages are stored in the crypto buffer; a maximum
of 256 messages can be stored in the crypto buffer.
CSMA/CD
=======
Carrier Sense Multiple Access/Collision Detection. A method of handling
network access of several stations on a Local Area Network (LAN).
Collision Detection (CD) is a refine- ment of this method whereby a
station on a LAN detects and compensates for the undesirable collisions
that could mix data when several stations try to transmit
simultaneously.
CSR
===
Control Status Register.
CTA
===
Control Table Area. A memory segment (segment E) that contains
descriptors of a slot's running configuration, such as, which segments
are in use, the host numbers are assigned to that slot, and the number
of ports are available to each host in that slot. See slot.
See also segment.
CTS
===
Clear To Send. A signal sent by the DCE to the DTE notifying the DTE
that it can begin to transmit data. Contrast with Request To Send (RTS)
CUD
===
Controlling User Directory. A collection of all user validation data
(username, password, and network access). Accessed by NETVAL, the CUD
is periodically copied to the Master User Directory (MUD) of each
Supervisor in the network.
CUG
===
Closed User Group. A group that can only receive data from or transmit
data to other users within the same group.
Customer Premise Equipment (CPE)
================================
Equipment located at a customer site; the equipment might not be owned
by the customer.
Cyclic Redundancy Check (CRC)
=============================
An error-detection technique used to check the accuracy of frames
transmitted over a data link. A mathematical calculation performed by
Node Code to ensure data integrity of the packets transmitted between
nodes.
Cyclopean Gateway Service (CGS)
===============================
A BT North America online electronic library that offers access to
thousands of publications.
