<s>
The	O
System/38	B-Device
has	O
48-bit	O
addressing	O
,	O
which	O
was	O
unique	O
for	O
the	O
time	O
,	O
and	O
a	O
novel	O
integrated	O
database	B-Application
system	I-Application
.	O
</s>
<s>
It	O
was	O
oriented	O
toward	O
a	O
multi-user	B-Operating_System
system	I-Operating_System
environment	O
.	O
</s>
<s>
Although	O
the	O
System/38	B-Device
failed	O
to	O
displace	O
the	O
systems	O
it	O
was	O
intended	O
to	O
replace	O
,	O
its	O
architecture	O
served	O
as	O
the	O
basis	O
of	O
the	O
much	O
more	O
successful	O
IBM	B-Device
AS/400	I-Device
.	O
</s>
<s>
The	O
System/38	B-Device
was	O
introduced	O
on	O
October	O
24	O
,	O
1978	O
and	O
delivered	O
in	O
1980	O
.	O
</s>
<s>
The	O
architecture	O
shared	O
many	O
similarities	O
with	O
the	O
design	O
of	O
the	O
failed	O
IBM	B-Device
Future	I-Device
Systems	I-Device
project	I-Device
,	O
including	O
the	O
single-level	B-Device
store	I-Device
,	O
the	O
use	O
of	O
microcode	B-Device
to	O
implement	O
operating	O
system	O
functionality	O
,	O
and	O
the	O
Machine	O
Interface	O
abstraction	O
.	O
</s>
<s>
The	O
president	O
of	O
IBM	O
's	O
General	O
Systems	O
Division	O
(	O
GSD	O
)	O
said	O
at	O
the	O
time	O
:	O
"	O
The	O
System/38	B-Device
is	O
the	O
largest	O
program	O
we	O
've	O
ever	O
introduced	O
in	O
GSD	O
and	O
it	O
is	O
one	O
of	O
the	O
top	O
three	O
or	O
four	O
largest	O
programs	O
ever	O
introduced	O
in	O
IBM.	O
"	O
</s>
<s>
The	O
system	O
was	O
designed	O
as	O
a	O
follow-on	O
for	O
the	O
System/3	B-Device
,	O
but	O
it	O
is	O
not	O
compatible	O
with	O
those	O
computers	O
.	O
</s>
<s>
The	O
predecessors	O
to	O
the	O
System/38	B-Device
include	O
the	O
System/3	B-Device
(	O
1969	O
)	O
,	O
System/32	B-Device
(	O
1975	O
)	O
,	O
and	O
System/34	B-Device
(	O
1977	O
)	O
.	O
</s>
<s>
In	O
1983	O
the	O
System/36	B-Device
was	O
released	O
as	O
a	O
low-end	O
business	O
computer	O
for	O
users	O
who	O
found	O
the	O
System/38	B-Device
too	O
expensive	O
for	O
their	O
needs	O
.	O
</s>
<s>
The	O
System/38	B-Device
was	O
succeeded	O
by	O
the	O
IBM	B-Device
AS/400	I-Device
midrange	B-Device
computer	I-Device
family	O
in	O
1988	O
,	O
which	O
originally	O
used	O
a	O
processor	O
architecture	O
similar	O
to	O
the	O
System/38	B-Device
,	O
before	O
adopting	O
PowerPC-based	O
processors	O
in	O
1995	O
.	O
</s>
<s>
The	O
IBM	O
5381	O
System	B-General_Concept
Unit	I-General_Concept
contains	O
processor	O
,	O
main	O
memory	O
,	O
disk	O
storage	O
,	O
a	O
diskette	O
magazine	O
drive	O
,	O
and	O
a	O
system	B-Device
console	I-Device
with	O
keyboard	O
and	O
a	O
display	O
.	O
</s>
<s>
The	O
IBM	O
5382	O
System	B-General_Concept
Unit	I-General_Concept
is	O
physically	O
identical	O
to	O
5381	O
,	O
but	O
with	O
more	O
powerful	O
processors	O
,	O
more	O
memory	O
,	O
and	O
more	O
disk	O
storage	O
.	O
</s>
<s>
Users	O
typically	O
interacted	O
with	O
the	O
system	O
through	O
IBM	B-Device
5250	I-Device
series	O
terminals	O
.	O
</s>
<s>
The	O
system	O
includes	O
a	O
central	B-General_Concept
processing	I-General_Concept
unit	I-General_Concept
with	O
512K	O
,	O
768K	O
,	O
1024K	O
,	O
1280K	O
,	O
or	O
1536K	O
bytes	O
of	O
main	O
storage	O
.	O
</s>
<s>
It	O
includes	O
a	O
memory	B-General_Concept
management	I-General_Concept
unit	I-General_Concept
supporting	O
demand	B-General_Concept
paging	I-General_Concept
,	O
used	O
by	O
the	O
system	O
software	O
to	O
implement	O
a	O
single-level	B-Device
store	I-Device
architecture	O
.	O
</s>
<s>
The	O
System/38	B-Device
CPU	O
features	O
a	O
48-bit	O
address	O
space	O
,	O
which	O
was	O
selected	O
as	O
a	O
compromise	O
between	O
64-bit	B-Device
addressing	O
,	O
which	O
certain	O
IBM	O
engineers	O
wanted	O
for	O
the	O
sake	O
of	O
future	O
proofing	O
,	O
and	O
32-bit	O
addressing	O
,	O
which	O
other	O
engineers	O
wanted	O
for	O
cost	O
saving	O
purposes	O
.	O
</s>
<s>
The	O
System/38	B-Device
console	B-Device
incorporates	O
a	O
keyboard	O
and	O
a	O
display	O
screen	O
with	O
16	O
lines	O
of	O
64	O
characters	O
,	O
inconsistent	O
with	O
the	O
locally	O
attached	O
5250	B-Device
terminals	O
,	O
which	O
are	O
either	O
12x40	O
or	O
24x80	O
,	O
depending	O
on	O
model	O
.	O
</s>
<s>
The	O
keyboard	O
is	O
available	O
to	O
the	O
system	O
operator	O
to	O
enter	O
Control	B-Operating_System
Language	I-Operating_System
commands	O
.	O
</s>
<s>
The	O
System/38	B-Device
and	O
its	O
descendants	O
use	O
a	O
machine	O
interface	O
architecture	O
to	O
isolate	O
the	O
application	B-Application
software	I-Application
and	O
most	O
of	O
the	O
operating	O
system	O
from	O
hardware	O
dependencies	O
,	O
including	O
such	O
details	O
as	O
address	O
size	O
and	O
register	O
size	O
.	O
</s>
<s>
Compilers	B-Language
for	O
System/38	B-Device
and	O
its	O
successors	O
generate	O
code	O
in	O
a	O
high-level	O
instruction	B-General_Concept
set	I-General_Concept
known	O
as	O
the	O
Machine	O
Interface	O
,	O
or	O
MI	O
.	O
</s>
<s>
MI	O
is	O
a	O
virtual	O
instruction	B-General_Concept
set	I-General_Concept
;	O
it	O
is	O
not	O
the	O
instruction	B-General_Concept
set	I-General_Concept
of	O
the	O
underlying	O
CPU	O
.	O
</s>
<s>
Unlike	O
some	O
other	O
virtual-machine	O
architectures	O
in	O
which	O
the	O
virtual	O
instructions	O
are	O
interpreted	O
at	O
runtime	O
(	O
see	O
P-code	B-Language
machine	I-Language
)	O
,	O
MI	O
instructions	O
are	O
never	O
interpreted	O
.	O
</s>
<s>
They	O
constitute	O
an	O
intermediate	O
compile	B-Language
time	O
step	O
and	O
are	O
translated	O
into	O
the	O
processor	O
's	O
instruction	B-General_Concept
set	I-General_Concept
as	O
the	O
final	O
compilation	B-Language
step	O
.	O
</s>
<s>
If	O
a	O
program	O
is	O
moved	O
from	O
a	O
processor	O
with	O
one	O
native	O
instruction	B-General_Concept
set	I-General_Concept
to	O
a	O
processor	O
with	O
another	O
native	O
instruction	B-General_Concept
set	I-General_Concept
,	O
the	O
MI	O
instructions	O
will	O
be	O
re-translated	O
into	O
the	O
native	O
instruction	B-General_Concept
set	I-General_Concept
of	O
the	O
new	O
machine	O
before	O
the	O
program	O
is	O
executed	O
for	O
the	O
first	O
time	O
on	O
the	O
new	O
machine	O
.	O
</s>
<s>
The	O
TIMI	O
(	O
Technology	O
Independent	O
Machine	O
Interface	O
)	O
of	O
OS/400	B-Application
is	O
a	O
backwards	O
compatible	O
extension	O
of	O
the	O
System/38	B-Device
MI	O
.	O
</s>
<s>
As	O
a	O
result	O
,	O
it	O
is	O
possible	O
for	O
a	O
program	O
originally	O
developed	O
on	O
a	O
System/38	B-Device
to	O
run	O
on	O
current	O
IBM	B-Application
i	I-Application
hardware	O
without	O
ever	O
being	O
recompiled	B-Language
.	O
</s>
<s>
IBM	O
referred	O
to	O
all	O
code	O
below	O
the	O
Machine	O
Interface	O
layer	O
of	O
the	O
System/38	B-Device
architecture	O
as	O
microcode	B-Device
,	O
and	O
treated	O
it	O
as	O
part	O
of	O
the	O
hardware	O
.	O
</s>
<s>
The	O
term	O
microcode	B-Device
was	O
used	O
to	O
cover	O
a	O
wide	O
array	O
of	O
low-level	O
code	O
,	O
ranging	O
from	O
traditional	O
microcode	B-Device
,	O
up	O
to	O
functionality	O
typically	O
associated	O
with	O
the	O
kernels	B-Operating_System
of	O
other	O
operating	O
systems	O
,	O
as	O
well	O
as	O
the	O
implementation	O
of	O
the	O
integrated	O
database	O
.	O
</s>
<s>
There	O
were	O
two	O
levels	O
of	O
microcode	B-Device
in	O
the	O
System/38	B-Device
:	O
</s>
<s>
Horizontal	O
Microcode	B-Device
(	O
HMC	O
)	O
,	O
which	O
implemented	O
a	O
register-memory/memory	O
-memory	O
instruction	B-General_Concept
set	I-General_Concept
architecture	I-General_Concept
known	O
as	O
the	O
internal	O
microprogramming	B-Device
(	O
IMP	O
)	O
instruction	B-General_Concept
set	I-General_Concept
or	O
the	O
Internal	O
Microprogrammed	O
Interface	O
(	O
IMPI	O
)	O
using	O
the	O
native	O
microcode	B-Device
of	O
the	O
System/38	B-Device
'	O
s	O
processor	O
.	O
</s>
<s>
process	O
)	O
scheduling	O
and	O
message	O
passing	O
were	O
implemented	O
directly	O
in	O
microcode	B-Device
as	O
part	O
of	O
the	O
Horizontal	O
Microcode	B-Device
.	O
</s>
<s>
The	O
Horizontal	O
Microcode	B-Device
resided	O
in	O
control	B-General_Concept
store	I-General_Concept
;	O
it	O
corresponded	O
to	O
traditional	O
microcode	B-Device
.	O
</s>
<s>
Vertical	O
Microcode	B-Device
(	O
VMC	O
)	O
,	O
which	O
implemented	O
the	O
Machine	O
Interface	O
in	O
terms	O
of	O
the	O
IMPI	O
architecture	O
;	O
this	O
was	O
implemented	O
by	O
translating	O
MI	O
code	O
into	O
IMPI	O
code	O
and	O
executing	O
it	O
.	O
</s>
<s>
The	O
Vertical	O
Microcode	B-Device
resided	O
in	O
main	O
memory	O
.	O
</s>
<s>
The	O
use	O
of	O
the	O
term	O
microcode	B-Device
stemmed	O
from	O
a	O
1969	O
antitrust	O
case	O
against	O
IBM	O
which	O
resulted	O
in	O
IBM	O
unbundling	O
software	O
from	O
its	O
hardware	O
products	O
(	O
i.e.	O
</s>
<s>
By	O
treating	O
the	O
low	O
level	O
code	O
of	O
the	O
System/38	B-Device
as	O
part	O
of	O
the	O
hardware	O
,	O
IBM	O
was	O
able	O
to	O
treat	O
the	O
MI	O
as	O
the	O
native	O
instruction	B-General_Concept
set	I-General_Concept
of	O
the	O
System/38	B-Device
,	O
and	O
thus	O
have	O
the	O
freedom	O
to	O
change	O
the	O
IMPI	O
and	O
microcode	B-Device
as	O
the	O
underlying	O
hardware	O
evolved	O
.	O
</s>
<s>
Early	O
AS/400	B-Device
systems	O
inherited	O
the	O
System/38	B-Device
microcode	B-Device
structure	O
,	O
but	O
the	O
term	O
microcode	B-Device
was	O
dropped	O
,	O
leading	O
IBM	O
to	O
rename	O
the	O
layers	O
to	O
the	O
Vertical	O
Licensed	O
Internal	O
Code	O
and	O
Horizontal	O
Licensed	O
Internal	O
Code	O
.	O
</s>
<s>
The	O
operating	O
system	O
of	O
the	O
System/38	B-Device
is	O
the	O
Control	B-Operating_System
Program	I-Operating_System
Facility	I-Operating_System
(	O
CPF	O
)	O
.	O
</s>
<s>
CPF	O
is	O
not	O
related	O
to	O
the	O
System	B-Operating_System
Support	I-Operating_System
Program	I-Operating_System
operating	O
system	O
of	O
the	O
IBM	B-Device
System/34	I-Device
and	O
System/36	B-Device
.	O
</s>
<s>
While	O
CPF	O
is	O
considered	O
to	O
be	O
the	O
operating	O
system	O
of	O
the	O
System/38	B-Device
,	O
it	O
sits	O
on	O
top	O
of	O
the	O
System/38	B-Device
Machine	O
Interface	O
layer	O
,	O
and	O
consequently	O
much	O
of	O
the	O
traditional	O
operating	O
system	O
functionality	O
of	O
the	O
platform	O
is	O
implemented	O
in	O
the	O
Horizontal	O
and	O
Vertical	O
Microcode	B-Device
.	O
</s>
<s>
The	O
System/38	B-Device
also	O
has	O
the	O
distinction	O
of	O
being	O
the	O
first	O
commercially	O
available	O
IBM	B-Device
Midrange	I-Device
computer	I-Device
to	O
have	O
a	O
database	B-Application
management	I-Application
system	I-Application
(	O
DBMS	O
)	O
integrated	O
into	O
the	O
operating	O
system	O
.	O
</s>
<s>
The	O
operational	O
control	B-Operating_System
language	I-Operating_System
of	O
the	O
System/38	B-Device
is	O
called	O
CL	B-Operating_System
,	O
for	O
Control	B-Operating_System
Language	I-Operating_System
.	O
</s>
<s>
CL	B-Operating_System
programs	O
,	O
similar	O
in	O
concept	O
to	O
shell	B-Language
scripts	I-Language
,	O
can	O
be	O
compiled	B-Language
and	O
executed	O
natively	B-Language
.	O
</s>
<s>
The	O
System/38	B-Device
was	O
designed	O
with	O
security	O
built	O
in	O
as	O
part	O
of	O
its	O
architecture	O
.	O
</s>
<s>
This	O
has	O
been	O
continued	O
and	O
expanded	O
throughout	O
the	O
AS/400	B-Device
and	O
iSeries	B-Device
computer	O
lines	O
.	O
</s>
<s>
The	O
System/38	B-Device
was	O
superseded	O
by	O
the	O
AS/400	B-Device
,	O
which	O
also	O
provided	O
compatibility	O
with	O
System/36	B-Device
data	O
and	O
software	O
.	O
</s>
<s>
S/38	B-Device
programs	O
with	O
'	O
observability	O
 '	O
intact	O
,	O
that	O
is	O
source	O
code	O
embedded	O
within	O
the	O
compiled	B-Language
binary	O
executive	O
at	O
the	O
expense	O
of	O
larger	O
compiled	B-Language
object	O
sizes	O
,	O
can	O
still	O
run	O
on	O
the	O
AS/400	B-Device
and	O
successor	O
systems	O
as	O
the	O
restore	O
option	O
incorporates	O
a	O
recompile	B-Language
for	O
the	O
then	O
back-version	O
source	O
.	O
</s>
<s>
However	O
,	O
most	O
proprietary	O
vendor	O
application	O
libraries	O
of	O
objects	O
were	O
compiled	B-Language
without	O
such	O
'	O
observability	O
 '	O
and	O
require	O
original	O
vendor	O
replacement	O
and	O
consequent	O
expense	O
when	O
upgrading	O
to	O
an	O
AS/400	B-Device
.	O
</s>
<s>
IBM	O
sold	O
an	O
estimated	O
20,000	O
System/38s	B-Device
within	O
the	O
first	O
five	O
years	O
of	O
availability	O
,	O
according	O
to	O
articles	O
published	O
in	O
industry	O
magazines	O
NEWS	O
34/38	O
and	O
Midrange	O
Computing	O
.	O
</s>
<s>
Although	O
billed	O
as	O
a	O
minicomputer	B-Architecture
,	O
the	O
S/38	B-Device
was	O
much	O
more	O
expensive	O
than	O
IBM	O
's	O
established	O
best-selling	O
System/34	B-Device
,	O
and	O
its	O
replacement	O
,	O
the	O
System/36	B-Device
.	O
</s>
<s>
Of	O
equal	O
importance	O
was	O
the	O
difficulty	O
of	O
upgrading	O
from	O
a	O
System/34	B-Device
to	O
a	O
S/38	B-Device
.	O
</s>
<s>
IBM	O
tacitly	O
acknowledged	O
this	O
by	O
bringing	O
out	O
the	O
System/36	B-Device
–	O
an	O
upgraded	O
System/34	B-Device
–	O
after	O
the	O
launch	O
of	O
the	O
S/38	B-Device
.	O
</s>
<s>
Although	O
the	O
System/38	B-Device
did	O
not	O
sell	O
in	O
large	O
numbers	O
,	O
it	O
commanded	O
a	O
higher	O
profit	O
margin	O
than	O
IBM	O
's	O
other	O
midrange	B-Device
systems	I-Device
,	O
and	O
thus	O
was	O
a	O
profitable	O
product	O
line	O
for	O
IBM	O
.	O
</s>
<s>
The	O
System/34	B-Device
,	O
the	O
System/38	B-Device
and	O
the	O
mainframe	O
System/370	B-Device
architecture	O
.	O
</s>
<s>
Digital	O
Equipment	O
Corporation	O
,	O
at	O
that	O
time	O
one	O
of	O
IBM	O
's	O
main	O
competitors	O
,	O
was	O
able	O
to	O
exploit	O
this	O
by	O
offering	O
a	O
wide	O
range	O
of	O
products	O
based	O
on	O
a	O
single	O
architecture	O
-	O
specifically	O
the	O
VAX	B-Device
architecture	O
.	O
</s>
<s>
IBM	O
's	O
counter	O
to	O
this	O
,	O
the	O
9370	B-Device
,	O
was	O
a	O
commercial	O
failure	O
,	O
and	O
at	O
that	O
time	O
,	O
The	O
New	O
York	O
Times	O
wrote	O
,	O
sales	O
of	O
the	O
System/36	B-Device
and	O
System/38	B-Device
were	O
"	O
lagging.	O
"	O
</s>
