<s>
The	O
IBM	B-Device
System/3	I-Device
was	O
an	O
IBM	B-Device
midrange	I-Device
computer	I-Device
introduced	O
in	O
1969	O
,	O
and	O
marketed	O
until	O
1985	O
.	O
</s>
<s>
It	O
was	O
produced	O
by	O
IBM	O
Rochester	O
in	O
Minnesota	O
as	O
a	O
low-end	O
business	O
computer	O
aimed	O
at	O
smaller	O
organizations	O
that	O
still	O
used	O
IBM	B-Device
1400	I-Device
series	I-Device
computers	O
or	O
unit	O
record	O
equipment	O
.	O
</s>
<s>
The	O
first	O
member	O
of	O
what	O
IBM	O
refers	O
to	O
as	O
their	O
"	O
midrange	O
"	O
line	O
,	O
it	O
also	O
introduced	O
the	O
RPG	B-Language
II	I-Language
programming	O
language	O
.	O
</s>
<s>
It	O
is	O
the	O
first	O
ancestor	O
in	O
the	O
product	O
line	O
whose	O
current	O
version	O
is	O
the	O
IBM	B-Application
i	I-Application
series	O
and	O
includes	O
the	O
highly	O
successful	O
AS/400	B-Device
.	O
</s>
<s>
At	O
its	O
launch	O
in	O
1969	O
it	O
was	O
available	O
for	O
$	O
1000/month	O
—	O
less	O
than	O
half	O
cost	O
of	O
an	O
IBM	B-Device
System/360	I-Device
Model	I-Device
20	I-Device
;	O
the	O
smallest	O
member	O
of	O
the	O
IBM	B-Application
System/360	I-Application
family	O
.	O
</s>
<s>
Many	O
of	O
the	O
original	O
System/3	B-Device
model	I-Device
10	I-Device
units	O
were	O
shipped	O
diskless	O
,	O
with	O
only	O
the	O
new	O
IBM	O
5424	O
Multifunction	O
Card	O
Unit	O
(	O
MFCU	O
)	O
which	O
read	O
,	O
punched	O
,	O
printed	O
on	O
and	O
sorted	O
the	O
new	O
,	O
smaller	O
96-column	O
punched	B-Architecture
cards	I-Architecture
introduced	O
at	O
the	O
same	O
time	O
.	O
</s>
<s>
The	O
System/3	B-Device
and	O
successor	O
models	O
System/32	B-Device
,	O
System/34	B-Device
,	O
System/36	B-Device
and	O
System/38	B-Device
are	O
generally	O
referred	O
to	O
in	O
IBM	O
terminology	O
as	O
"	B-Device
midrange	I-Device
systems	I-Device
"	I-Device
—	O
in	O
contrast	O
to	O
IBM	B-Device
's	I-Device
mainframes	I-Device
.	O
</s>
<s>
The	O
IBM	B-Device
System/3	I-Device
was	O
announced	O
as	O
a	O
computer	O
system	O
that	O
initially	O
consisted	O
of	O
:	O
</s>
<s>
For	O
mass	O
storage	O
,	O
the	O
System/3	B-Device
used	O
the	O
IBM	B-Device
5444	I-Device
single-platter	O
disk	B-Device
,	O
roughly	O
the	O
size	O
of	O
a	O
large	O
pizza	O
;	O
initially	O
each	O
platter	O
held	O
2.5	O
MB	O
of	O
data	O
.	O
</s>
<s>
Standard	O
configuration	O
for	O
storage	O
was	O
one	O
or	O
two	O
fixed	B-Device
disks	I-Device
,	O
each	O
in	O
a	O
separate	O
pull-out	O
drawer	O
,	O
which	O
typically	O
held	O
the	O
operating	O
system	O
and	O
user-developed	O
programs	O
.	O
</s>
<s>
Additionally	O
,	O
each	O
fixed	O
disc	O
could	O
have	O
a	O
removable	O
cartridge	O
disk	B-Device
attached	O
;	O
these	O
typically	O
contained	O
the	O
data-files	O
associated	O
with	O
various	O
applications	O
,	O
for	O
example	O
Payroll	O
,	O
and	O
users	O
frequently	O
had	O
a	O
number	O
of	O
them	O
.	O
</s>
<s>
The	O
System/3	B-Device
was	O
also	O
available	O
with	O
the	O
IBM	O
5445	O
disk	B-Device
drive	O
(	O
20mb	O
)	O
and	O
later	O
the	O
model	O
15	O
allowed	O
"	O
winchester	O
"	O
style	O
3340	O
drives	O
.	O
</s>
<s>
Other	O
companies	O
such	O
as	O
Memorex	O
manufactured	O
compatible	O
5445	O
drives	O
for	O
the	O
System/3	B-Device
.	O
</s>
<s>
The	O
most	O
common	O
punched-card	B-Architecture
device	O
was	O
IBM	O
5424	O
Multifunction	O
Card	O
Unit	O
(	O
MFCU	O
)	O
which	O
read	O
,	O
punched	O
,	O
printed	O
on	O
and	O
sorted	O
the	O
new	O
,	O
smaller	O
96-column	O
punched	B-Architecture
cards	I-Architecture
.	O
</s>
<s>
Instead	O
of	O
the	O
rectangular	O
punches	O
in	O
the	O
classic	O
80-column	O
IBM	B-Architecture
card	I-Architecture
,	O
the	O
new	O
cards	O
had	O
tiny	O
(	O
1mm	O
)	O
,	O
circular	O
holes	O
much	O
like	O
paper	O
tape	O
.	O
</s>
<s>
Data	O
was	O
stored	O
in	O
six-bit	O
binary-coded	O
decimal	O
code	O
,	O
with	O
three	O
rows	O
of	O
32	O
characters	O
each	O
,	O
or	O
in	O
8-bit	O
EBCDIC	B-Language
,	O
with	O
the	O
two	O
extra	O
holes	O
located	O
in	O
the	O
top	O
rows	O
.	O
</s>
<s>
They	O
were	O
about	O
1/3	O
the	O
size	O
of	O
the	O
older	O
80	B-Architecture
column	I-Architecture
cards	O
but	O
held	O
20%	O
more	O
text	O
data	O
.	O
</s>
<s>
Available	O
as	O
RPQs	O
(	O
special	O
order	O
equipment	O
)	O
to	O
handle	O
80-column	O
cards	O
were	O
the	O
IBM	O
2560	O
Multifunction	O
Card	O
Machine	O
(	O
MFCM	O
)	O
which	O
could	O
read	O
,	O
punch	O
,	O
interpret	O
and	O
sort	O
,	O
and	O
the	O
IBM	B-Device
1442	I-Device
which	O
could	O
only	O
read	O
and	O
punch	O
.	O
</s>
<s>
Offline	O
storage	O
was	O
available	O
with	O
the	O
purchase	O
of	O
an	O
external	O
tape	O
drive	O
which	O
read	O
and	O
wrote	O
standard	O
IBM	O
9-track	B-Device
tape	I-Device
.	O
</s>
<s>
The	O
System/3	B-Device
Mod	O
10	O
optionally	O
included	O
the	O
IBM	O
3410	O
magnetic	O
tape	O
subsystem	O
.	O
</s>
<s>
The	O
System/3	B-Device
Operator	O
Console	O
Facility	O
(	O
OCF	O
)	O
consisted	O
of	O
either	O
a	O
modified	O
IBM	O
Selectric	O
typewriter	O
interfaced	O
into	O
the	O
computer	O
,	O
or	O
a	O
special	O
purpose	O
IBM	B-Operating_System
3270	I-Operating_System
display	O
.	O
</s>
<s>
Later	O
on	O
,	O
IBM	O
offered	O
multiple	O
models	O
of	O
the	O
existing	O
IBM	B-Device
1403	I-Device
printer	O
line	O
,	O
which	O
had	O
been	O
originally	O
built	O
for	O
the	O
IBM	B-Device
1401	I-Device
computer	O
.	O
</s>
<s>
With	O
the	O
arrival	O
of	O
the	O
IBM	B-Device
3740	I-Device
data	O
entry	O
system	O
,	O
the	O
System/3	B-Device
Model	I-Device
10	I-Device
got	O
a	O
feature	O
called	O
LCA	O
(	O
local	O
communication	O
adaptor	O
)	O
which	O
allowed	O
an	O
IBM	B-Device
3741	I-Device
station	O
to	O
be	O
"	O
attached	O
"	O
to	O
the	O
system	O
to	O
transmit/receive	O
data	O
.	O
</s>
<s>
Later	O
models	O
of	O
the	O
System/3	B-Device
such	O
as	O
the	O
Model	O
8	O
were	O
cardless	O
and	O
used	O
the	O
8	O
"	O
3740	O
style	O
floppy	O
disk	B-Device
.	O
</s>
<s>
The	O
instruction	B-General_Concept
set	I-General_Concept
was	O
optimised	O
for	O
two	O
key	O
aspects	O
of	O
the	O
product	O
:	O
limited	O
availability	O
of	O
main	O
memory	O
,	O
and	O
the	O
RPG	B-Language
II	I-Language
programming	O
language	O
.	O
</s>
<s>
For	O
programmers	O
used	O
to	O
IBM	B-Device
mainframe	I-Device
behaviour	O
,	O
this	O
meant	O
that	O
the	O
S/3	O
branch	O
operation	O
could	O
be	O
likened	O
to	O
a	O
conditional	O
BALR	O
(	O
branch	O
and	O
link	O
register	O
)	O
–	O
very	O
useful	O
when	O
branching	O
to	O
a	O
sub-routine	O
,	O
and	O
returning	O
after	O
it	O
had	O
processed	O
.	O
</s>
<s>
All	O
the	O
above	O
got	O
more	O
complicated	O
with	O
the	O
System/3	B-Device
model	O
15	O
,	O
and	O
the	O
Systems/34	O
and	O
/36	O
.	O
</s>
<s>
A	O
simple	O
job	B-Application
control	I-Application
language	I-Application
called	O
Operation	O
Control	O
Language	O
(	O
OCL	O
)	O
was	O
superficially	O
similar	O
to	O
the	O
Job	B-Application
Control	I-Application
Language	I-Application
(	O
JCL	O
)	O
.	O
</s>
<s>
The	O
System/3	B-Device
supported	O
RPG	B-Language
II	I-Language
,	O
Fortran	O
IV	O
,	O
COBOL	B-Application
,	O
and	O
Assembler	B-Language
.	O
</s>
<s>
The	O
System/3	B-Device
came	O
standard	O
with	O
a	O
RPG	B-Language
II	I-Language
compiler	O
.	O
</s>
<s>
In	O
a	O
card-only	O
system	O
,	O
the	O
RPG	B-Language
II	I-Language
compiler	O
was	O
supplied	O
as	O
two	O
phases	O
.	O
</s>
<s>
The	O
System/3	B-Device
had	O
no	O
provision	O
for	O
halting	O
a	O
process	O
once	O
it	O
had	O
started	O
to	O
run	O
.	O
</s>
<s>
Error	O
codes	O
were	O
displayed	O
on	O
a	O
two-digit	O
seven-segment	B-General_Concept
display	I-General_Concept
(	O
one	O
of	O
the	O
first	O
seen	O
,	O
and	O
built	O
with	O
lamps	O
rather	O
than	O
LEDs	O
)	O
.	O
</s>
<s>
The	O
range	O
of	O
error	O
codes	O
included	O
not	O
only	O
decimal	O
and	O
hexadecimal	O
digits	O
(	O
as	O
seven-segment	B-General_Concept
displays	I-General_Concept
are	O
commonly	O
used	O
)	O
but	O
also	O
a	O
limited	O
set	O
of	O
other	O
letters	O
;	O
for	O
example	O
,	O
"	O
P3	O
"	O
was	O
one	O
of	O
several	O
printer	O
error	O
codes	O
.	O
</s>
<s>
A	O
thick	O
manual	O
that	O
came	O
with	O
the	O
System/3	B-Device
aided	O
the	O
operator	O
in	O
interpreting	O
the	O
error	O
codes	O
and	O
suggested	O
recovery	O
procedures	O
.	O
</s>
<s>
The	O
System/3	B-Device
had	O
no	O
audible	O
warning	O
device	O
,	O
so	O
a	O
program	O
that	O
was	O
not	O
printing	O
,	O
reading	O
cards	O
,	O
or	O
causing	O
other	O
obvious	O
activity	O
could	O
halt	O
and	O
the	O
operator	O
would	O
not	O
know	O
it	O
unless	O
they	O
happened	O
to	O
look	O
at	O
the	O
status	O
display	O
.	O
</s>
<s>
The	O
concept	O
of	O
keying	O
your	O
punched	B-Architecture
cards	I-Architecture
through	O
the	O
console	O
was	O
a	O
marketing	O
ploy	O
.	O
</s>
<s>
In	O
reality	O
,	O
the	O
System/3	B-Device
could	O
not	O
be	O
a	O
computer	O
and	O
a	O
keypunch	O
at	O
the	O
same	O
time	O
,	O
so	O
when	O
it	O
was	O
a	O
keypunch	O
,	O
no	O
computing	O
was	O
possible	O
.	O
</s>
<s>
The	O
original	O
IBM	B-Device
System/3	I-Device
,	O
which	O
was	O
shown	O
in	O
July	O
1969	O
,	O
had	O
the	O
keypunch	O
console	O
so	O
they	O
could	O
offer	O
a	O
computer	O
for	O
under	O
$	O
2,000	O
/month	O
.	O
</s>
<s>
This	O
took	O
the	O
'	O
heavy	O
lifting	O
 '	O
off	O
of	O
the	O
MFCU	O
and	O
freed	O
the	O
System/3	B-Device
for	O
actual	O
computing	O
functions	O
.	O
</s>
<s>
Most	O
experienced	O
System/3	B-Device
users	O
minimized	O
use	O
of	O
the	O
MFCU	O
as	O
much	O
as	O
possible	O
,	O
since	O
it	O
was	O
a	O
system	O
bottleneck	O
.	O
</s>
<s>
The	O
later	O
System/32	B-Device
,	O
IBM	B-Device
System/34	I-Device
and	O
IBM	B-Device
System/36	I-Device
were	O
all	O
able	O
to	O
run	O
System/3	B-Device
applications	O
through	O
emulation	O
.	O
</s>
<s>
The	O
System/32	B-Device
used	O
a	O
vertically	O
microcoded	B-Device
processor	O
,	O
with	O
16-bit	O
microcode	B-Device
words	O
,	O
which	O
emulated	O
the	O
System/3	B-Device
instruction	B-General_Concept
set	I-General_Concept
,	O
rather	O
slowly	O
,	O
in	O
microcode	B-Device
.	O
</s>
<s>
The	O
System/34	B-Device
and	O
System/36	B-Device
both	O
had	O
two	O
processors	O
:	O
a	O
Control	O
Storage	O
Processor	O
(	O
CSP	O
)	O
,	O
as	O
in	O
System/32	B-Device
,	O
which	O
handled	O
most	O
supervisor	O
and	O
input/output	O
operations	O
,	O
and	O
a	O
Main	O
Storage	O
Processor	O
(	O
MSP	O
)	O
.	O
</s>
<s>
This	O
latter	O
was	O
a	O
re-implementation	O
of	O
the	O
System/3	B-Device
model	O
15	O
processor	O
;	O
effectively	O
providing	O
"	O
hardware	O
emulation	O
"	O
of	O
the	O
System/3	B-Device
.	O
</s>
