IBM 3174 Reference Manual page 210

device. A mechanical, electrical, or.electronic
contrivance with a specific purpose.
display field. (1) An area In the display buffer that
contains a set of characters that can be manipulated or
operated upon as a unit. (2) A group of consecutive
characters (In the buffer) that starts with an attribute
character (defining the characteristics of the field) and
contains one or more alphanumeric characters. The
field continues to, but does not Include, the next
attribute character.
display station. An Input/output device containing a
display screen and an attached keyboard that allows a
user to send Information to or receive Information from
the system.
duplex. Pertaining to communication In which data
can be sent and received at the same time.
Synonymous with full duplex.
EIA communication adapter. A communication adapter
conforming to EIA standards that can combine and
send Information on two lines at speeds up to 19.2
kbps.
EIA 232D. An electrical Interface defined by the
Electronics Industries Association for establishing
connections and controlling data flow between data
terminal equipment and data communication
equipment. The Interface has been adapted to allow
communication between DTEs.
emulate. (1) To Imitate one system with another,
primarily by hardware, so that the Imitating system
accepts the same data, executes the same computer
programs, and achieves the same results as the
Imitated computer system.
emulation. (1) The Imitation of all or part of one
system by another, primarily by hardware, so that the
Imitating system accepts the same data, executes the
same programs, and achieves the same results as the
Imitated computer system. (2) The use of
programming techniques and special machine features
to permit a computing system to execute programs
written for another system. (3) Imitation; for example,
Imitation of a computer or device. (4) See terminal
emulation. (5) Contrast with simulation.
field. See display field.
flow control. (1) In data communication, control of the
data transfer rate. (2) In SNA, the process of managing
the rate at which data traffic passes between
components of the network. The purpose of flow
control Is to optimize the rate of flow of message units
with minimum congestion In the network, that Is,
neither to overflow the buffers at the receiver or at
Intermediate routing nodes nor to leave the receiver
waiting for more message units. (3) The methods used
to control the flow of Information across a network.
foreground logical terminal (LT). Synonym for active
logical terminal (LT).
full duplex. Synonym for duplex.
H
half-duplex. In data communication, pertaining to
transmission In only one direction at a time. Contrast
with duplex.
hertz (Hz). A unit of frequency equal to 1 cycle per
second.
host computer. (1) In a computer network, a computer
that provides end users with services such as
computation and data bases and that usually performs
network control functions. (2) The primary or
controlling computer In a multiple-computer
Installation. (3) A computer used to prepare programs
for use on another computer or on another data
processing system; for example, a computer used to
compile link edit, or test programs to be used on
another system. (4) Synonym for host processor.
host processor. (1) A processor that controls all or
part of a user application network. (2) In a network,
the processing unit In which resides the access method
for the network. (3) In an SNA network, the processing
unit that contains a system services control point
(SSCP). (4) A processing unit that executes the access
method for attached communication controllers.
(5) The processing unit required to create and maintain
PSS. (6) Synonymous with host computer.
host system. (1) A data processing system used to
prepare programs and operating environments for use
on another computer or controller. (2) The data
processing system to which a network Is connected and
with which the system can communicate. (3) The
controlling or highest-level system in a data
communication configuration; for example, a System/38
Is the host system for the work stations connected to It.
K
keyboard mapping. A table that defines which
keyboard sequences are equivalent to functions on
another keyboard.
Glossary X-5