<s>
The	O
IBM	B-Device
709	I-Device
was	O
a	O
computer	O
system	O
,	O
initially	O
announced	O
by	O
IBM	O
in	O
January	O
1957	O
and	O
first	O
installed	O
during	O
August	O
1958	O
.	O
</s>
<s>
The	O
709	O
was	O
an	O
improved	O
version	O
of	O
its	O
predecessor	O
,	O
the	O
IBM	B-Device
704	I-Device
,	O
and	O
was	O
the	O
third	O
of	O
the	O
IBM	O
700/7000	O
series	O
of	O
scientific	O
computers	O
.	O
</s>
<s>
The	O
improvements	O
included	O
overlapped	O
input/output	O
,	O
indirect	B-Language
addressing	I-Language
,	O
and	O
three	O
"	O
convert	O
"	O
instructions	O
which	O
provided	O
support	O
for	O
decimal	B-Application
arithmetic	O
,	O
leading	O
zero	O
suppression	O
,	O
and	O
several	O
other	O
operations	O
.	O
</s>
<s>
An	O
optional	O
hardware	O
emulator	B-Application
executed	O
old	O
IBM	B-Device
704	I-Device
programs	O
on	O
the	O
IBM	B-Device
709	I-Device
.	O
</s>
<s>
This	O
was	O
the	O
first	O
commercially	O
available	O
emulator	B-Application
.	O
</s>
<s>
Registers	O
and	O
most	O
704	O
instructions	O
were	O
emulated	B-Application
in	O
709	O
hardware	O
.	O
</s>
<s>
Complex	O
704	O
instructions	O
such	O
as	O
floating	B-Algorithm
point	I-Algorithm
trap	O
and	O
input-output	O
routines	O
were	O
emulated	B-Application
in	O
709	O
software	O
.	O
</s>
<s>
IBM	O
announced	O
a	O
transistorized	O
version	O
of	O
the	O
709	O
,	O
called	O
the	O
IBM	B-Device
7090	I-Device
,	O
in	O
1958	O
,	O
only	O
a	O
year	O
after	O
the	O
announcement	O
of	O
the	O
709	O
,	O
thus	O
cutting	O
short	O
the	O
709	O
's	O
product	O
life	O
.	O
</s>
<s>
The	O
IBM	B-Device
709	I-Device
has	O
a	O
38-bit	O
accumulator	O
,	O
a	O
36-bit	O
multiplier	O
quotient	O
register	O
,	O
and	O
three	O
15-bit	O
index	B-General_Concept
registers	I-General_Concept
whose	O
contents	O
are	O
subtracted	O
from	O
the	O
base	O
address	O
instead	O
of	O
being	O
added	O
to	O
it	O
.	O
</s>
<s>
All	O
three	O
index	B-General_Concept
registers	I-General_Concept
can	O
participate	O
in	O
an	O
instruction	O
:	O
the	O
3-bit	O
tag	O
field	O
in	O
the	O
instruction	O
is	O
a	O
bit	O
map	O
specifying	O
which	O
of	O
the	O
registers	O
participate	O
in	O
the	O
operation	O
,	O
however	O
if	O
more	O
than	O
one	O
index	B-General_Concept
register	I-General_Concept
is	O
specified	O
,	O
their	O
contents	O
are	O
combined	O
by	O
a	O
logical	O
or	O
operation	O
,	O
not	O
addition.p.	O
</s>
<s>
Some	O
also	O
subtract	O
the	O
decrement	O
field	O
from	O
the	O
contents	O
of	O
the	O
index	B-General_Concept
registers	I-General_Concept
.	O
</s>
<s>
One	O
(	O
STR	O
,	O
instruction	O
code	O
binary	O
101	O
)	O
was	O
not	O
implemented	O
until	O
the	O
IBM	B-Device
709	I-Device
.	O
</s>
<s>
Fixed	O
point	O
numbers	O
are	O
stored	O
in	O
binary	O
sign/magnitude	B-Algorithm
format	I-Algorithm
.	O
</s>
<s>
Whereas	O
I/O	O
on	O
704	O
is	O
a	O
programmed	O
function	O
of	O
the	O
central	O
processor	O
-	O
data	O
words	O
are	O
transferred	O
to	O
or	O
from	O
the	O
I/O	O
register	O
,	O
one	O
at	O
a	O
time	O
,	O
using	O
a	O
"	O
copy	O
"	O
instruction	O
-	O
the	O
709	O
uses	O
the	O
IBM-766	B-Device
Data	O
Synchronizer	O
,	O
which	O
provides	O
two	O
independently	O
"	O
programmed	O
"	O
I/O	O
channels	O
.	O
</s>
<s>
Up	O
to	O
three	O
Data	O
Synchronizers	O
can	O
be	O
attached	O
to	O
a	O
709	O
,	O
each	O
able	O
to	O
control	O
up	O
to	O
20	O
IBM	B-Device
729	I-Device
tape	O
drives	O
and	O
an	O
IBM	B-Device
716	I-Device
alphanumeric	O
line	O
printer	O
,	O
IBM	B-Device
711	I-Device
card-reader	O
and	O
721	O
card	O
punch	O
.	O
</s>
<s>
Up	O
to	O
two	O
IBM	O
733	O
Magnetic	B-General_Concept
Drum	I-General_Concept
units	O
,	O
each	O
with	O
8,192	O
words	O
of	O
memory	O
,	O
could	O
be	O
attached	O
independently	O
from	O
the	O
Data	O
Synchronizers	O
.	O
</s>
<s>
The	O
709	O
could	O
initially	O
load	O
programs	O
(	O
boot	B-Operating_System
)	O
from	O
card	O
,	O
tape	O
or	O
drum	O
.	O
</s>
<s>
The	O
IBM	B-Device
738	I-Device
Magnetic	O
Core	O
Storage	O
used	O
on	O
709	O
was	O
also	O
a	O
milestone	O
of	O
hybrid	O
technology	O
.	O
</s>
