The IBM System/360 is a solid-state, program com
patible, data processing system providing the speed,
precision, and data manipulating versatility demand
ed by the challenge of commerce, science, and in
dustry.System/360, with advanced logical design im
plemented by microminiature technology, provides a
new dimension of performance, flexibility, and relia
bility. This dimension makes possible a new, more
efficient systems approach to all areas of information
processing, with economy of implementation and ease
of use.System/360 is a single, coordinated set of new
data processing components intended to replace the
old logical structure with an advanced creative de
sign for present and future application.
The logical design ofSystem/360 permits efficient
use at several levels of performance with the preser
vation of upward and downward program compati
bility. Extremely high performance and reliability re
quirements are met by combining several models into
one multisystem using the multisystem feature.
General-Purpose DesignSystem/360 is a general-purpose system designed to
be tailored for commercial, scientific, communications,
or control applications. AStandard instruction set pro
vides the basic computing function of the system.. To
this set a decimal feature may be added to provide a
Commercial instruction set or a floating-point feature
may be added to provide aScientific instruction set.
When the storage protection feature is added to the
commercial and scientific features, aUniversal set is
obtained. Direct control and timer features may be
added to satisfy requirements forTELE-PROCESSINC@ systems to allow load-sharing or to satisfy real-time
needs.System/360 can accommodate large quantities of
addressable storage. The markedly increased capaci
ties over other present storage is provided by the
combined use of high-speed storage of medium size
and large-capacity storage of medium speed. Thus,
the requirements for both performance and size are
satisfied in one system by incorporating a heirarchy
of storage units. The design also anticipates future
development of even greater storage capacities.Sys tem/360 incorporates a standard method for attaching
input/output devices differing in function, data rate,IBM System/360
and access time. An individualSystem/360 is obtained
by selecting the system components most suited to the
applications from a wide variety of alternatives in in
ternal performance, functional ability, and input/out
put(I/O). Models of System/360 differ in storage speed, width
(the amount of data obtained in each instruction ac
cess), register width, and capability of simultaneous
processing. Yet these differences do not affect the logi
cal appearance ofSystem/360 to the programmer. Several cpu's permit a wide choice in internal per
formance. The range is such that the ratio of internal
performances between the largest and the smallest
model is approximately50 for scientific computation
and 15 for commercial processing.
Compatibility
All models ofSystem/360 are upward and downward
program compatible, that is, any program gives identi
cal results on any model. Compatibility allows for
ease in systems growth, convenience in systems back
up, and simplicity in education.
The compatibility rule has three limitations.
1. The systems facilities used by a program should
be the same in each case. Thus, the optionalCPU fea
tures and the storage capacity, as well as the quantity,
type, and priority ofI/O equipment, should be equiva
lent.
2. The program should be independent of the re
lation of instruction execution times and ofI/O data
rates, access times, and command execution times.
3. The compatibility rule does not apply to detail
functions for which neither frequency of occurrence
nor usefulness of result warrants identical action in
all models. These functions, all explicitly identified in
this manual, are concerned with the handling of in
valid programs and machine malfunctions.
System Program
Interplay of equipment and program is an essential
consideration inSystem/360. The system is designed
to operate with a supervisory program that coordi
nates and executes allI/O instructions, handles excep
tional conditions, and supervises scheduling and exe
cution of multiple programs.System/360 provides for
IBM System/360 5
patible, data processing system providing the speed,
precision, and data manipulating versatility demand
ed by the challenge of commerce, science, and in
dustry.
plemented by microminiature technology, provides a
new dimension of performance, flexibility, and relia
bility. This dimension makes possible a new, more
efficient systems approach to all areas of information
processing, with economy of implementation and ease
of use.
data processing components intended to replace the
old logical structure with an advanced creative de
sign for present and future application.
The logical design of
use at several levels of performance with the preser
vation of upward and downward program compati
bility. Extremely high performance and reliability re
quirements are met by combining several models into
one multisystem using the multisystem feature.
General-Purpose Design
be tailored for commercial, scientific, communications,
or control applications. A
vides the basic computing function of the system
this set a decimal feature may be added to provide a
Commercial instruction set or a floating-point feature
may be added to provide a
When the storage protection feature is added to the
commercial and scientific features, a
obtained. Direct control and timer features may be
added to satisfy requirements for
needs.
addressable storage. The markedly increased capaci
ties over other present storage is provided by the
combined use of high-speed storage of medium size
and large-capacity storage of medium speed. Thus,
the requirements for both performance and size are
satisfied in one system by incorporating a heirarchy
of storage units. The design also anticipates future
development of even greater storage capacities.
input/output devices differing in function, data rate,
and access time. An individual
by selecting the system components most suited to the
applications from a wide variety of alternatives in in
ternal performance, functional ability, and input/out
put
(the amount of data obtained in each instruction ac
cess), register width, and capability of simultaneous
processing. Yet these differences do not affect the logi
cal appearance of
formance. The range is such that the ratio of internal
performances between the largest and the smallest
model is approximately
and 15 for commercial processing.
Compatibility
All models of
program compatible, that is, any program gives identi
cal results on any model. Compatibility allows for
ease in systems growth, convenience in systems back
up, and simplicity in education.
The compatibility rule has three limitations.
1. The systems facilities used by a program should
be the same in each case. Thus, the optional
tures and the storage capacity, as well as the quantity,
type, and priority of
lent.
2. The program should be independent of the re
lation of instruction execution times and of
rates, access times, and command execution times.
3. The compatibility rule does not apply to detail
functions for which neither frequency of occurrence
nor usefulness of result warrants identical action in
all models. These functions, all explicitly identified in
this manual, are concerned with the handling of in
valid programs and machine malfunctions.
System Program
Interplay of equipment and program is an essential
consideration in
to operate with a supervisory program that coordi
nates and executes all
tional conditions, and supervises scheduling and exe
cution of multiple programs.
IBM System/360 5