<s>
The	O
IBM	B-Device
System/360	I-Device
Model	I-Device
30	I-Device
was	O
a	O
low-end	O
member	O
of	O
the	O
IBM	B-Application
System/360	I-Application
family	O
.	O
</s>
<s>
The	O
Model	O
30	O
was	O
a	O
popular	O
IBM	B-Device
mainframe	I-Device
which	O
was	O
announced	O
in	O
1964	O
as	O
the	O
least	O
powerful	O
of	O
the	O
System/360s	B-Application
.	O
</s>
<s>
The	O
System/360	B-Application
series	O
was	O
the	O
first	O
line	O
of	O
computers	O
in	O
the	O
world	O
to	O
allow	O
machine	O
language	O
programs	O
to	O
be	O
written	O
that	O
could	O
be	O
used	O
across	O
a	O
broad	O
range	O
of	O
compatible	O
machines	O
of	O
different	O
sizes	O
.	O
</s>
<s>
It	O
was	O
the	O
smallest	O
model	O
that	O
had	O
the	O
full	O
System/360	B-Application
instruction	O
set	O
(	O
unlike	O
the	O
Model	B-Device
20	I-Device
)	O
and	O
served	O
as	O
a	O
stand-alone	O
system	O
,	O
communications	O
system	O
or	O
as	O
a	O
satellite	O
processor	O
of	O
a	O
larger	O
system	O
.	O
</s>
<s>
Along	O
with	O
the	O
360/40	B-Device
,	O
these	O
were	O
the	O
two	O
largest	O
revenue	O
producing	O
System/360	B-Application
models	O
,	O
accounting	O
for	O
over	O
half	O
the	O
System/360	B-Application
units	O
sold	O
.	O
</s>
<s>
The	O
two	O
were	O
cosmetically	O
different	O
;	O
the	O
30-1	O
looked	O
like	O
other	O
System/360	B-Application
models	O
,	O
with	O
indicator	O
lamps	O
exposed	O
on	O
the	O
front	O
panel	O
and	O
labeled	O
,	O
but	O
the	O
30-2	O
took	O
a	O
retrograde	O
design	O
step	O
,	O
putting	O
the	O
lights	O
behind	O
a	O
stencil	O
,	O
as	O
they	O
had	O
been	O
on	O
pre-360	O
machines	O
like	O
the	O
IBM	B-Device
1401	I-Device
.	O
</s>
<s>
The	O
7th	O
edition	O
of	O
IBM	B-Application
System/360	I-Application
Basic	B-Application
Operating	I-Application
System	I-Application
Programmer	O
's	O
Guide	O
,	O
dated	O
September	O
1967	O
,	O
lists	O
first	O
among	O
major	O
changes	O
support	O
for	O
"	O
an	O
intermediate	O
storage	O
size	O
(	O
24K	O
)	O
for	O
System/360	B-Application
Model	O
30.	O
"	O
</s>
<s>
emulated	B-Application
by	O
the	O
microprogram	B-Device
.	I-Device
</s>
<s>
The	O
microcode	B-Device
was	O
stored	O
in	O
CCROS	O
(	O
Card	O
Capacitor	O
Read-Only	O
Storage	O
)	O
developed	O
in	O
Endicott	O
.	O
</s>
<s>
The	O
Model	O
30	O
and	O
Model	O
40	O
were	O
originally	O
supposed	O
to	O
share	O
the	O
transformer	B-General_Concept
read-only	I-General_Concept
storage	I-General_Concept
(	O
TROS	O
)	O
being	O
developed	O
at	O
IBM	O
Hursley	O
,	O
but	O
CCROS	O
was	O
cheaper	O
to	O
manufacture	O
.	O
</s>
<s>
This	O
system	O
used	O
Mylar	O
cards	O
the	O
size	O
and	O
shape	O
of	O
a	O
standard	O
IBM	O
punched-card	B-Architecture
,	O
so	O
the	O
microcode	B-Device
could	O
be	O
changed	O
using	O
a	O
keypunch	B-Device
.	O
</s>
<s>
Each	O
card	O
held	O
720	O
bits	O
,	O
and	O
the	O
total	O
microcode	B-Device
consisted	O
of	O
4032	O
60-bit	O
words	O
.	O
</s>
<s>
Operating	B-General_Concept
System	I-General_Concept
choices	O
:	O
</s>
<s>
BOS	O
(	O
Basic	B-Application
Operating	I-Application
System	I-Application
)	O
required	O
a	O
disk	O
drive	O
,	O
but	O
,	O
like	O
BPS	O
,	O
could	O
run	O
on	O
the	O
smallest	O
360/30	O
,	O
the	O
8K	O
model	O
C30	O
.	O
</s>
<s>
TOS	O
(	O
Tape	O
Operating	B-General_Concept
System	I-General_Concept
)	O
,	O
as	O
the	O
name	O
suggests	O
,	O
required	O
a	O
tape	O
drive	O
but	O
no	O
disk	O
.	O
</s>
<s>
DOS	O
(	O
Disk	O
Operating	B-General_Concept
System	I-General_Concept
)	O
was	O
a	O
popular	O
choice	O
for	O
the	O
360/30	O
.	O
</s>
<s>
Amazingly	O
the	O
smaller	O
BOS	O
had	O
a	O
Spooling	B-Device
system	O
for	O
queued	O
printing	O
,	O
whereas	O
DOS	O
did	O
not	O
until	O
the	O
arrival	O
in	O
the	O
late	O
1960s	O
of	O
"	O
an	O
add-on	O
component	O
called	O
POWER.	O
"	O
</s>
<s>
Programming	O
was	O
mostly	O
in	O
the	O
COBOL	B-Application
,	O
RPG	B-Language
and	O
Assembler	B-Language
languages	I-Language
for	O
the	O
commercial	O
applications	O
which	O
were	O
the	O
predominant	O
uses	O
of	O
this	O
computer	O
.	O
</s>
<s>
Fortran	B-Application
could	O
also	O
be	O
used	O
for	O
the	O
scientific	O
and	O
engineering	O
applications	O
,	O
and	O
a	O
PL/I	B-Language
subset	O
compiler	O
PL/I	B-Language
( D	O
)	O
was	O
available	O
.	O
</s>
<s>
COBOL	B-Application
programs	O
for	O
other	O
computers	O
could	O
be	O
run	O
after	O
recompiling	O
on	O
the	O
System/360	B-Application
,	O
except	O
that	O
the	O
INPUT-OUTPUT	O
SECTION	O
had	O
to	O
be	O
re-written	O
to	O
describe	O
to	O
the	O
System/360	B-Application
device	O
assignments	O
.	O
</s>
<s>
Although	O
the	O
instruction	O
set	O
of	O
System/360	B-Application
was	O
not	O
backward	B-General_Concept
compatible	I-General_Concept
with	O
earlier	O
systems	O
,	O
IBM	O
provided	O
emulators	B-Application
for	O
the	O
earlier	O
systems	O
.	O
</s>
<s>
With	O
the	O
additional	O
Compatibility	O
Feature	O
hardware	O
and	O
Compatibility	O
Support	O
software	O
under	O
DOS/360	O
,	O
the	O
IBM	O
1401/1440/1460	O
object	O
programs	O
could	O
be	O
run	O
in	O
the	O
emulation	B-Application
mode	O
,	O
with	O
little	O
or	O
no	O
reprogramming	O
.	O
</s>
<s>
Although	O
the	O
360/30	O
could	O
be	O
configured	O
to	O
emulate	O
an	O
IBM	B-Device
1620	I-Device
,	O
two	O
factors	O
made	O
it	O
less	O
crucial	O
than	O
the	O
above	O
IBM	O
1400	O
series	O
emulation	B-Application
:	O
</s>
<s>
The	O
IBM	B-Device
1130	I-Device
was	O
the	O
preferred	O
successor	O
to	O
the	O
IBM	B-Device
1620	I-Device
.	O
</s>
<s>
Fortran	B-Application
accounted	O
for	O
a	O
significant	O
part	O
of	O
how	O
the	O
1620	O
was	O
used	O
,	O
and	O
IBM	B-Device
1620	I-Device
Fortran	B-Application
programs	O
could	O
be	O
converted	O
to	O
run	O
on	O
System/360	B-Application
.	O
</s>
