h
hard
copy:
A printed copy
of
machine
output
in
a visually readable form, for ex·
ample, a printed recording
of
the
messages displayed on
the
System/370
Model 125
video display unit.
hard
stop:
A condition, usually caused by an error,
in
which
the
CPU
is
stopped and
is
not
executing
the
microprogram .
.
I
IC
(instruction counter): Hardware circuit which tells
the
central processor (CPU)
the
main storage address
at
which it will find
the
next
instruction
to
execute.
inclusive segments: Overlay segments
in
the
same region
that
can be
in
main storage
simu Itaneously. .
index (data management):
1.
A table
in
the
catalog structure used
to
locate data
sets. 2. A table used
to
locate
the
records
of
an indexed sequential data set.
initial program loading (lPL): The initialization procedure which loads
the
nucleus and
begins normal operations.
initiator:
The
part
of
the job scheduler
that
selects jobs and job steps
to
be executed,
allocates
input/output
devices for
them,
places them under task control, and
at
completion
of
the
job, supplies control information for writing job
output
on a system
output
unit.
input
queue: A queue of job definitions
in
direct access storage, assigned
to
a job class
and arranged
in
assigned priority order, waiting
to
be processed.
input stream: Job· control statements entering
the
system; may also include input data.
installation: A particular computing system,
in
terms
of
the
overall work it does and
the
people who manage it, operate it, apply it
to
problems, service it, and use
the
resu Its it produces.
interrupt: A break
in
the
normal sequence ·of instruction execution. It causes an
automatic transfer
to
a preset storage location where appropriate action
is
taken.
invalid page:
In
S/370,
a page
that
cannot
be directly addressed
by
the
dynamic
address translation feature
of
the
central processing unit.
I/O area: An area (portion)
of
real storage into which data
is
read or from which data
is
written;
the
term buffer
is
often used
in
place
of
I/O area.
I/O Trace
(Input/Output
Trace): A program
that
records I/O device activity for all
or
a selected group of I/O devices.
10CS
(input/output
control system): A group of macro instruction routines provided
by I
BM
for handling
the
transfer
of
data between main storage and external storage
devices.
irrecoverable error: A hardware error which
cannot
be recovered from
by
the
normal
hardware and retry procedures .
.
J
job:
1.
A unit
of
work for
the
system from the
standpoint
of
installation accounting
and control. A job consists of one
or
more job steps. 2. A collection
of
related
problem programs, identified
in
the
input stream by a JOB
statement
followed by one
or
more EXEC statements.
job control starernent: A control statement
in
the
input stream
that
identifies a job
or
defines its needs.
job library: A set
of
user· identified partitioned data sets used as
the
main source
of
load modules for a given job.
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