<s>
The	O
SWAC	B-Device
(	O
Standards	B-Device
Western	I-Device
Automatic	I-Device
Computer	I-Device
)	O
was	O
an	O
early	O
electronic	O
digital	O
computer	O
built	O
in	O
1950	O
by	O
the	O
U.S.	O
National	O
Bureau	O
of	O
Standards	O
(	O
NBS	O
)	O
in	O
Los	O
Angeles	O
,	O
California	O
.	O
</s>
<s>
Like	O
the	O
SEAC	B-Device
which	O
was	O
built	O
about	O
the	O
same	O
time	O
,	O
the	O
SWAC	B-Device
was	O
a	O
small-scale	O
interim	O
computer	O
designed	O
to	O
be	O
built	O
quickly	O
and	O
put	O
into	O
operation	O
while	O
the	O
NBS	O
waited	O
for	O
more	O
powerful	O
computers	O
to	O
be	O
completed	O
(	O
in	O
particular	O
,	O
the	O
RAYDAC	B-Device
by	O
Raytheon	O
)	O
.	O
</s>
<s>
It	O
had	O
256	O
words	O
of	O
memory	B-General_Concept
,	O
using	O
Williams	B-General_Concept
tubes	I-General_Concept
,	O
with	O
each	O
word	O
being	O
37	O
bits	O
.	O
</s>
<s>
Several	O
years	O
later	O
,	O
drum	B-General_Concept
memory	I-General_Concept
was	O
added	O
.	O
</s>
<s>
When	O
the	O
SWAC	B-Device
was	O
completed	O
in	O
August	O
1950	O
,	O
it	O
was	O
the	O
fastest	O
computer	O
in	O
the	O
world	O
.	O
</s>
<s>
It	O
continued	O
to	O
hold	O
that	O
status	O
until	O
the	O
IAS	B-Device
computer	I-Device
was	O
completed	O
a	O
year	O
later	O
.	O
</s>
<s>
In	O
January	O
1952	O
,	O
Raphael	O
M	O
.	O
Robinson	O
used	O
the	O
SWAC	B-Device
to	O
discover	O
five	O
Mersenne	O
primes	O
—	O
the	O
largest	O
prime	O
numbers	O
known	O
at	O
the	O
time	O
,	O
with	O
157	O
,	O
183	O
,	O
386	O
,	O
664	O
and	O
687	O
digits	O
.	O
</s>
<s>
Additionally	O
,	O
the	O
SWAC	B-Device
was	O
vital	O
in	O
doing	O
the	O
intense	O
calculation	O
required	O
for	O
the	O
X-ray	O
analysis	O
of	O
the	O
structure	O
of	O
vitamin	O
B12	O
done	O
by	O
Dorothy	O
Hodgkin	O
.	O
</s>
