Asynchronous Serial Communications Programmer's Reference Manual (32022-90052)

Glossary 307
Glossary
character (normally [CTRL]-Y) is
entered during execution of a
program with subsystem break
enabled.
cross-validate The process of
assuring that information
contained in two locations is
consistent where it is imperative
that it be consistent. For example,
an automatic cross validation
occurs when you enter SYSGEN
to assure that information
contained in NMCONFIG.PUB.SYS
agrees with system configuration
data.
CSMA/CD Carrier Sense
Multiple Access with Collision
Detect, transmission access
method used by the IEEE 802.3
LAN standard.
CSN See circuit-switching
network.
CTB The cache transfer bus in
the backplane of an HP 3000.
CUG See closed user group.
D
data Basic elements of
information that can be processed
or produced by a computer.
Datacommunications and
Terminal controller See DTC.
datagram A self contained
packet that is independent of
other packets. It does not require
an acknowledgment and it carries
information which is sufficient to
route it from one DTE to another
DTE without relying on earlier
exchange between the DTEs.
data overrun Transmitted data
that is sent faster than the
receiving equipment can receive
it. The resultant overflow data is
lost. See also flow control.
Datapac The national public
PSN of Canada.
Datex-P The national public
PSN of West Germany.
D bit Delivery confirmation bit.
Used in the X.25 protocol, the
setting of the D bit in DATA
packets indicates whether
delivery acknowledgment of the
packet is required from the local
DCE or from the remote DTE. It
therefore allows the choice
between local and end-to-end
acknowledgment.
DCE Data circuit terminating
equipment. The interfacing
equipment required in order to
interface to data terminal
equipment (DTE) and its
transmission circuit. Synonyms:
data communications equipment,
dataset. A modem is an example
of a DCE.
DDX The national public PSN of
Japan.
DDFA DTC Device File Access
Utilities. A set of HP-UX utilities
which is used by systems and
user written applications to
programmatically access devices
attached to DTC ports.