<s>
The	O
IBM	B-Device
Selective	I-Device
Sequence	I-Device
Electronic	I-Device
Calculator	I-Device
(	O
SSEC	O
)	O
was	O
an	O
electromechanical	O
computer	O
built	O
by	O
IBM	O
.	O
</s>
<s>
During	O
World	O
War	O
II	O
,	O
International	O
Business	O
Machines	O
Corporation	O
(	O
IBM	O
)	O
funded	O
and	O
built	O
an	O
Automatic	B-Device
Sequence	I-Device
Controlled	I-Device
Calculator	I-Device
(	O
ASCC	O
)	O
for	O
Howard	O
H	O
.	O
Aiken	O
at	O
Harvard	O
University	O
.	O
</s>
<s>
The	O
machine	O
,	O
formally	O
dedicated	O
in	O
August	O
1944	O
,	O
was	O
widely	O
known	O
as	O
the	O
Harvard	B-Device
Mark	I-Device
I	I-Device
.	O
</s>
<s>
The	O
February	O
1946	O
announcement	O
of	O
the	O
fully	O
electronic	O
ENIAC	B-Device
energized	O
the	O
project	O
.	O
</s>
<s>
The	O
new	O
machine	O
,	O
called	O
the	O
IBM	B-Device
Selective	I-Device
Sequence	I-Device
Electronic	I-Device
Calculator	I-Device
(	O
SSEC	O
)	O
,	O
was	O
ready	O
to	O
be	O
installed	O
by	O
August	O
1947	O
.	O
</s>
<s>
Approximately	O
12,500	O
vacuum	O
tubes	O
were	O
used	O
in	O
the	O
arithmetic	O
unit	O
,	O
control	O
,	O
and	O
its	O
eight	O
(	O
relatively	O
high-speed	O
)	O
registers	B-General_Concept
,	O
which	O
had	O
an	O
access	O
time	O
of	O
less	O
than	O
one	O
millisecond	O
.	O
</s>
<s>
About	O
21,400	O
relays	O
were	O
used	O
for	O
control	O
and	O
150	O
lower-speed	O
registers	B-General_Concept
,	O
with	O
an	O
access	O
time	O
of	O
20	O
milliseconds	O
.	O
</s>
<s>
The	O
arithmetic	B-General_Concept
logic	I-General_Concept
unit	I-General_Concept
of	O
the	O
SSEC	O
was	O
a	O
modified	O
IBM	B-Device
603	I-Device
electronic	O
multiplier	O
,	O
which	O
had	O
been	O
designed	O
by	O
James	O
W	O
.	O
Bryce	O
.	O
</s>
<s>
The	O
bulky	O
tubes	O
were	O
military	O
surplus	O
radar	B-Application
technology	O
,	O
which	O
filled	O
one	O
entire	O
wall	O
.	O
</s>
<s>
Addition	O
took	O
285	O
microseconds	O
and	O
multiplication	O
20	O
milliseconds	O
,	O
making	O
arithmetic	O
operations	O
much	O
faster	O
than	O
the	O
Harvard	B-Device
Mark	I-Device
I	I-Device
.	O
</s>
<s>
A	O
punched	B-Architecture
card	I-Architecture
reader	O
was	O
used	O
to	O
load	O
data	O
,	O
and	O
results	O
were	O
produced	O
on	O
punched	B-Architecture
cards	I-Architecture
or	O
high-speed	O
printers	O
.	O
</s>
<s>
The	O
19-digit	O
word	O
was	O
stored	O
on	O
the	O
card	O
stock	O
tape	O
or	O
registers	B-General_Concept
in	O
binary-coded	O
decimal	O
,	O
resulting	O
in	O
76	O
bits	O
,	O
with	O
two	O
extra	O
bits	O
for	O
indicating	O
positive	O
or	O
negative	O
sign	O
and	O
parity	O
,	O
while	O
the	O
two	O
side	O
rows	O
were	O
used	O
for	O
sprockets	O
.	O
</s>
<s>
The	O
familiar	O
80	B-Architecture
columns	I-Architecture
of	O
IBM	O
punched	B-Architecture
card	I-Architecture
technology	O
were	O
recorded	O
sideways	O
as	O
one	O
column	O
of	O
the	O
tape	O
.	O
</s>
<s>
ENIAC	B-Device
co-designer	O
J	O
.	O
Presper	O
Eckert	O
(	O
no	O
relation	O
to	O
the	O
IBM	O
Eckert	O
)	O
called	O
it	O
"	O
some	O
big	O
monstrosity	O
over	O
there	O
that	O
I	O
do	O
n't	O
think	O
ever	O
worked	O
right	O
"	O
.	O
</s>
<s>
Each	O
instruction	O
could	O
take	O
input	O
from	O
any	O
source	O
(	O
electronic	O
or	O
mechanical	O
registers	B-General_Concept
or	O
tape	O
readers	O
)	O
store	O
the	O
result	O
in	O
any	O
destination	O
(	O
electronic	O
or	O
mechanical	O
registers	B-General_Concept
,	O
tape	O
or	O
card	O
punch	O
or	O
printer	O
)	O
,	O
and	O
gave	O
the	O
address	O
of	O
the	O
next	O
instruction	O
,	O
which	O
could	O
also	O
be	O
any	O
source	O
.	O
</s>
<s>
For	O
each	O
new	O
program	O
,	O
tapes	O
and	O
card	B-Architecture
decks	I-Architecture
were	O
literally	O
"	O
loaded	O
"	O
on	O
the	O
readers	O
,	O
and	O
a	O
plugboard	O
changed	O
in	O
the	O
printer	O
to	O
modify	O
output	O
formatting	O
.	O
</s>
<s>
Robert	O
D	O
.	O
Richtmyer	O
of	O
Los	O
Alamos	O
National	O
Laboratory	O
used	O
the	O
SSEC	O
for	O
some	O
of	O
the	O
first	O
large-scale	O
applications	O
of	O
the	O
Monte	B-Algorithm
Carlo	I-Algorithm
method	I-Algorithm
.	O
</s>
<s>
The	O
SSEC	O
room	O
was	O
one	O
of	O
the	O
first	B-Architecture
computers	I-Architecture
to	O
use	O
a	O
raised	O
floor	O
,	O
so	O
visitors	O
would	O
not	O
see	O
unsightly	O
cables	O
or	O
trip	O
over	O
them	O
.	O
</s>
<s>
The	O
1946	O
ENIAC	B-Device
had	O
more	O
tubes	O
than	O
the	O
SSEC	O
and	O
was	O
faster	O
in	O
some	O
operations	O
,	O
but	O
was	O
originally	O
less	O
flexible	O
,	O
needing	O
to	O
be	O
rewired	O
for	O
each	O
new	O
problem	O
.	O
</s>
<s>
At	O
the	O
end	O
of	O
1948	O
a	O
new	O
IBM	B-Device
604	I-Device
multiplier	O
was	O
announced	O
,	O
which	O
used	O
newer	O
tube	O
technology	O
that	O
already	O
made	O
the	O
bulky	O
tubes	O
of	O
the	O
SSEC	O
obsolete	O
.	O
</s>
<s>
By	O
May	O
1949	O
the	O
Card-Programmed	B-Device
Electronic	I-Device
Calculator	I-Device
was	O
announced	O
,	O
and	O
shipped	O
in	O
September	O
.	O
</s>
<s>
Even	O
by	O
the	O
end	O
of	O
1948	O
,	O
the	O
limited	O
electronic	O
memory	O
of	O
the	O
SSEC	O
was	O
seen	O
as	O
a	O
problem	O
,	O
and	O
IBM	O
soon	O
licensed	O
the	O
Williams	B-General_Concept
tube	I-General_Concept
technology	O
developed	O
on	O
the	O
Manchester	B-Device
Baby	I-Device
at	O
the	O
Victoria	O
University	O
of	O
Manchester	O
.	O
</s>
<s>
Subsequent	O
computers	O
would	O
have	O
electronic	O
random	B-Architecture
access	I-Architecture
memory	I-Architecture
,	O
and	O
in	O
fact	O
the	O
ability	O
to	O
execute	O
instructions	O
from	O
processor	B-General_Concept
registers	I-General_Concept
was	O
generally	O
not	O
adopted	O
.	O
</s>
<s>
By	O
1951	O
the	O
Ferranti	B-Device
Mark	I-Device
I	I-Device
was	O
marketed	O
in	O
the	O
UK	O
as	O
a	O
commercial	O
computer	O
using	O
Williams	B-General_Concept
tube	I-General_Concept
technology	O
,	O
followed	O
by	O
the	B-Operating_System
UNIVAC	I-Operating_System
I	O
using	O
delay-line	O
memory	O
in	O
the	O
US	O
.	O
</s>
<s>
The	O
stored-program	O
concept	O
had	O
been	O
first	O
widely	O
published	O
in	O
1945	O
in	O
the	O
First	O
Draft	O
of	O
a	O
Report	O
on	O
the	O
EDVAC	B-Device
and	O
became	O
known	O
as	O
the	O
Von	B-Architecture
Neumann	I-Architecture
architecture	I-Architecture
.	O
</s>
<s>
The	O
EDVAC	B-Device
(	O
first	O
working	O
in	O
1949	O
)	O
was	O
the	O
ENIAC	B-Device
successor	O
,	O
designed	O
by	O
the	O
team	O
who	O
then	O
marketed	O
the	B-Operating_System
UNIVAC	I-Operating_System
.	O
</s>
<s>
An	O
IBM	B-Device
701	I-Device
computer	O
,	O
known	O
as	O
the	O
Defense	B-Device
Calculator	I-Device
,	O
was	O
installed	O
in	O
the	O
same	O
room	O
for	O
its	O
April	O
7	O
,	O
1953	O
,	O
public	O
debut	O
.	O
</s>
<s>
In	O
July	O
1953	O
the	O
much	O
less	O
expensive	O
(	O
and	O
even	O
better	O
selling	O
)	O
IBM	B-Device
650	I-Device
was	O
announced	O
,	O
which	O
had	O
been	O
developed	O
by	O
the	O
same	O
Endicott	O
team	O
who	O
developed	O
the	O
SSEC	O
.	O
</s>
