IBM System/370 Operator's Reference Manual page 239

main
page
pool: In DOSIVS, the set of all page frames in real storage not assigned to
the supervisor or one of the real partitions.
main storage: 1. The real address area of virtual storage. Contrast with auxiliary
storage. 2. All program addressable storage from which instructions may be executed
and from which data can be loaded directly into registers.
master scheduler: The part of the control program that responds to operator
commands and returns required information.
MCAR Maintenance Control Address Register
(Mod 165 and 168)
MCDR Maintenance Control Data Register
(Mod 165 and 168)
MCER Maintenance Control Entry Register
(Mod 165 and 168)
microprogram: A set of basic or elementary machine instructions that is loaded into
control storage to control CPU operations.
module (programming): A program unit that is input to, or output from, a single
execution of an assembler, compiler, or linkage editor; a source, object, or load
module.
move mode: A way of providing data by moving it instead of pointing to its location.
MRAR Maintenance Ripple Address Register
(Mod 165 and 168)
multijob operation: Concurrent execution of job steps from two or more jobs.
multiplexer channel: A channel designed to operate with a number of I/O devices
simultaneously on a byte basis. That is, several I/O devices can be transferring records
over the multiplexer channel, time-sharing it on a byte basis.
multiplexer mode: A means of transferring records to or from low·speed I/O devices
on the multiplexer channel, by interleaving bytes of data. The multiplexer channel
sustains simultaneous I/O operations on several subchannels. Bytes of data are inter·
leaved and then routed to or from the selected I/O devices or to and from the desired
locations in main storage. Multiplex mode is sometimes referred to as byte mode.
multiprogramming system: A system that controls more than one program simulta·
neously by interleaving their execution.
multitasking: The concurrent execution of one main task and one or more subtasks in
the same position.
n
name: A set of one to eight characters that identifies a statement, data set, module,
etc., and that is usually associated with the location of that which it identifies.
nucleus: That part of the control program that must always be present in main
storage. Also, the main storage area used by the nucleus and other transient control
program routines.
o
object module: The output of a single execution of an assembler or compiler, which
constitutes input to linkage editor. An object module consists of one or more control
sections in relocatable, though not executable, form and an associated control dictio-
nary.
offline: 1. • Pertaining to equipment or devices not under control of the central
processing unit. 2. Pertaining to program error diagnosis without using the computer
system (offline program debugging).
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