<s>
The	O
Manchester	B-Device
Baby	I-Device
,	O
also	O
called	O
the	O
Small-Scale	B-Device
Experimental	I-Device
Machine	I-Device
(	O
SSEM	O
)	O
,	O
was	O
the	O
first	O
electronic	O
stored-program	O
computer	O
.	O
</s>
<s>
The	O
Baby	O
was	O
not	O
intended	O
to	O
be	O
a	O
practical	O
computing	O
engine	O
,	O
but	O
was	O
instead	O
designed	O
as	O
a	O
testbed	O
for	O
the	O
Williams	B-General_Concept
tube	I-General_Concept
,	O
the	O
first	O
truly	O
random-access	B-Architecture
memory	I-Architecture
.	O
</s>
<s>
The	O
Mark	O
1	O
in	O
turn	O
quickly	O
became	O
the	O
prototype	O
for	O
the	O
Ferranti	B-Device
Mark	I-Device
1	I-Device
,	O
the	O
world	O
's	O
first	O
commercially	O
available	O
general-purpose	O
computer	O
.	O
</s>
<s>
The	O
Baby	O
had	O
a	O
32-bit	O
word	O
length	O
and	O
a	O
memory	B-General_Concept
of	O
32words	O
(	O
1	O
kilobit	O
,	O
1,024	O
bits	O
)	O
.	O
</s>
<s>
The	O
first	O
design	O
for	O
a	O
program-controlled	O
computer	O
was	O
Charles	O
Babbage	O
's	O
Analytical	B-Device
Engine	I-Device
in	O
the	O
1830s	O
,	O
with	O
Ada	B-General_Concept
Lovelace	I-General_Concept
conceiving	O
the	O
idea	O
of	O
the	O
first	O
theoretical	O
program	O
to	O
calculate	O
Bernoulli	O
numbers	O
.	O
</s>
<s>
A	O
century	O
later	O
,	O
in	O
1936	O
,	O
mathematician	O
Alan	O
Turing	O
published	O
his	O
description	O
of	O
what	O
became	O
known	O
as	O
a	O
Turing	B-Architecture
machine	I-Architecture
,	O
a	O
theoretical	O
concept	O
intended	O
to	O
explore	O
the	O
limits	O
of	O
mechanical	O
computation	O
.	O
</s>
<s>
Turing	O
proved	O
that	O
if	O
an	O
algorithm	O
can	O
be	O
written	O
to	O
solve	O
a	O
mathematical	O
problem	O
,	O
then	O
a	O
Turing	B-Architecture
machine	I-Architecture
can	O
execute	O
that	O
algorithm	O
.	O
</s>
<s>
Konrad	O
Zuse	O
's	O
Z3	B-Device
was	O
the	O
world	O
's	O
first	O
working	O
programmable	B-General_Concept
,	O
fully	O
automatic	O
computer	O
,	O
with	O
binary	O
digital	O
arithmetic	O
logic	O
,	O
but	O
it	O
lacked	O
the	O
conditional	O
branching	O
of	O
a	O
Turing	B-Architecture
machine	I-Architecture
.	O
</s>
<s>
On	O
12	O
May	O
1941	O
,	O
the	O
Z3	B-Device
was	O
successfully	O
presented	O
to	O
an	O
audience	O
of	O
scientists	O
of	O
the	O
Deutsche	O
Versuchsanstalt	O
für	O
Luftfahrt	O
(	O
"	O
German	O
Laboratory	O
for	O
Aviation	O
"	O
)	O
in	O
Berlin	O
.	O
</s>
<s>
The	O
Z3	B-Device
stored	O
its	O
program	O
on	O
an	O
external	O
tape	O
,	O
but	O
it	O
was	O
electromechanical	O
rather	O
than	O
electronic	O
.	O
</s>
<s>
The	O
earliest	O
electronic	O
computing	O
devices	O
were	O
the	B-Device
Atanasoff	I-Device
–	I-Device
Berry	I-Device
computer	I-Device
(	O
ABC	O
)	O
,	O
which	O
was	O
successfully	O
tested	O
in	O
1942	O
,	O
and	O
the	O
Colossus	B-Device
of	O
1943	O
,	O
but	O
neither	O
were	O
stored-program	O
machines	O
.	O
</s>
<s>
The	O
ENIAC	B-Device
(	O
1946	O
)	O
was	O
the	O
first	O
automatic	O
computer	O
that	O
was	O
both	O
electronic	O
and	O
general	O
purpose	O
.	O
</s>
<s>
It	O
was	O
Turing	B-Algorithm
complete	I-Algorithm
,	O
with	O
conditional	O
branching	O
,	O
and	O
programmable	B-General_Concept
to	O
solve	O
a	O
wide	O
range	O
of	O
problems	O
,	O
but	O
its	O
program	O
was	O
held	O
in	O
the	O
state	O
of	O
switches	O
in	O
patch	O
cords	O
,	O
rather	O
than	O
machine-changeable	O
memory	B-General_Concept
,	O
and	O
it	O
could	O
take	O
several	O
days	O
to	O
reprogram	O
.	O
</s>
<s>
Researchers	O
such	O
as	O
Turing	O
and	O
Zuse	O
investigated	O
the	O
idea	O
of	O
using	O
the	O
computer	O
's	O
memory	B-General_Concept
to	O
hold	O
the	O
program	O
as	O
well	O
as	O
the	O
data	O
it	O
was	O
working	O
on	O
,	O
and	O
it	O
was	O
mathematician	O
John	O
von	O
Neumann	O
who	O
wrote	O
a	O
widely	O
distributed	O
paper	O
describing	O
that	O
computer	O
architecture	O
,	O
still	O
used	O
in	O
almost	O
all	O
computers	O
.	O
</s>
<s>
The	O
construction	O
of	O
a	O
von	B-Architecture
Neumann	I-Architecture
computer	I-Architecture
depended	O
on	O
the	O
availability	O
of	O
a	O
suitable	O
memory	B-General_Concept
device	I-General_Concept
on	O
which	O
to	O
store	O
the	O
program	O
.	O
</s>
<s>
During	O
the	O
Second	O
World	O
War	O
researchers	O
working	O
on	O
the	O
problem	O
of	O
removing	O
the	O
clutter	O
from	O
radar	B-Application
signals	O
had	O
developed	O
a	O
form	O
of	O
delay-line	O
memory	B-General_Concept
,	O
the	O
first	O
practical	O
application	O
of	O
which	O
was	O
the	O
mercury	O
delay	O
line	O
,	O
developed	O
by	O
J	O
.	O
Presper	O
Eckert	O
.	O
</s>
<s>
Radar	B-Application
transmitters	O
send	O
out	O
regular	O
brief	O
pulses	O
of	O
radio	O
energy	O
,	O
the	O
reflections	O
from	O
which	O
are	O
displayed	O
on	O
a	O
CRT	B-Device
screen	I-Device
.	O
</s>
<s>
A	O
Mathematics	O
Division	O
was	O
set	O
up	O
at	O
the	O
NPL	O
,	O
and	O
on	O
19	O
February	O
1946	O
Alan	O
Turing	O
presented	O
a	O
paper	O
outlining	O
his	O
design	O
for	O
an	O
electronic	O
stored-program	O
computer	O
to	O
be	O
known	O
as	O
the	O
Automatic	B-Device
Computing	I-Device
Engine	I-Device
(	O
ACE	B-Device
)	O
.	O
</s>
<s>
At	O
about	O
the	O
same	O
time	O
,	O
EDVAC	B-Device
was	O
under	O
development	O
at	O
the	O
University	O
of	O
Pennsylvania	O
's	O
Moore	O
School	O
of	O
Electrical	O
Engineering	O
,	O
and	O
the	O
University	O
of	O
Cambridge	O
Mathematical	O
Laboratory	O
was	O
working	O
on	O
EDSAC	B-Device
.	O
</s>
<s>
The	O
NPL	O
did	O
not	O
have	O
the	O
expertise	O
to	O
build	O
a	O
machine	O
like	O
ACE	B-Device
,	O
so	O
they	O
contacted	O
Tommy	O
Flowers	O
at	O
the	O
General	O
Post	O
Office	O
's	O
(	O
GPO	O
)	O
Dollis	O
Hill	O
Research	O
Laboratory	O
.	O
</s>
<s>
Flowers	O
,	O
the	O
designer	O
of	O
Colossus	B-Device
,	O
the	O
world	O
's	O
first	O
programmable	B-General_Concept
electronic	O
computer	O
,	O
was	O
committed	O
elsewhere	O
and	O
was	O
unable	O
to	O
take	O
part	O
in	O
the	O
project	O
,	O
although	O
his	O
team	O
did	O
build	O
some	O
mercury	O
delay	O
lines	O
for	O
ACE	B-Device
.	O
</s>
<s>
The	O
government	O
department	O
responsible	O
for	O
the	O
NPL	O
decided	O
that	O
,	O
of	O
all	O
the	O
work	O
being	O
carried	O
out	O
by	O
the	O
TRE	O
on	O
its	O
behalf	O
,	O
ACE	B-Device
was	O
to	O
be	O
given	O
the	O
top	O
priority	O
.	O
</s>
<s>
Williams	O
led	O
a	O
TRE	O
development	O
group	O
working	O
on	O
CRT	O
stores	O
for	O
radar	B-Application
applications	O
,	O
as	O
an	O
alternative	O
to	O
delay	O
lines	O
.	O
</s>
<s>
Williams	O
was	O
not	O
available	O
to	O
work	O
on	O
the	O
ACE	B-Device
because	O
he	O
had	O
already	O
accepted	O
a	O
professorship	O
at	O
the	O
University	O
of	O
Manchester	O
,	O
and	O
most	O
of	O
his	O
circuit	O
technicians	O
were	O
in	O
the	O
process	O
of	O
being	O
transferred	O
to	O
the	O
Department	O
of	O
Atomic	O
Energy	O
.	O
</s>
<s>
Although	O
some	O
early	O
computers	O
such	O
as	O
EDSAC	B-Device
,	O
inspired	O
by	O
the	O
design	O
of	O
EDVAC	B-Device
,	O
later	O
made	O
successful	O
use	O
of	O
mercury	O
delay-line	O
memory	B-General_Concept
,	O
the	O
technology	O
had	O
several	O
drawbacks	O
:	O
it	O
was	O
heavy	O
,	O
it	O
was	O
expensive	O
,	O
and	O
it	O
did	O
not	O
allow	O
data	O
to	O
be	O
accessed	O
randomly	O
.	O
</s>
<s>
Williams	O
had	O
seen	O
an	O
experiment	O
at	O
Bell	O
Labs	O
demonstrating	O
the	O
effectiveness	O
of	O
cathode-ray	B-Device
tubes	I-Device
(	O
CRT	O
)	O
as	O
an	O
alternative	O
to	O
the	O
delay	O
line	O
for	O
removing	O
ground	O
echoes	O
from	O
radar	B-Application
signals	O
.	O
</s>
<s>
While	O
working	O
at	O
the	O
TRE	O
,	O
shortly	O
before	O
he	O
joined	O
the	O
University	O
of	O
Manchester	O
in	O
December	O
1946	O
,	O
he	O
and	O
Tom	O
Kilburn	O
had	O
developed	O
a	O
form	O
of	O
electronic	O
memory	B-General_Concept
known	O
as	O
the	O
Williams	B-General_Concept
tube	I-General_Concept
or	O
Williams	B-General_Concept
–	I-General_Concept
Kilburn	I-General_Concept
tube	I-General_Concept
,	O
based	O
on	O
a	O
standard	O
CRT	O
:	O
the	O
first	O
electronic	O
random-access	O
digital	O
storage	O
device	O
.	O
</s>
<s>
For	O
use	O
in	O
a	O
binary	O
digital	O
computer	O
,	O
the	O
tube	O
had	O
to	O
be	O
capable	O
of	O
storing	O
either	O
one	O
of	O
two	O
states	O
at	O
each	O
of	O
its	O
memory	B-General_Concept
locations	I-General_Concept
,	O
corresponding	O
to	O
the	O
binary	O
digits	O
(	O
bits	O
)	O
0	O
and1	O
.	O
</s>
<s>
It	O
exploited	O
the	O
positive	O
or	O
negative	O
electric	O
charge	O
generated	O
by	O
displaying	O
either	O
a	O
dash	O
or	O
a	O
dot	O
at	O
any	O
position	O
on	O
the	O
CRT	B-Device
screen	I-Device
,	O
a	O
phenomenon	O
known	O
as	O
secondary	O
emission	O
.	O
</s>
<s>
The	O
Williams	B-General_Concept
tube	I-General_Concept
used	O
in	O
Baby	O
was	O
based	O
on	O
the	O
CV1131	O
,	O
a	O
commercially	O
available	O
diameter	O
CRT	O
,	O
but	O
a	O
smaller	O
tube	O
,	O
the	O
CV1097	O
,	O
was	O
used	O
in	O
the	O
Mark	O
I	O
.	O
</s>
<s>
After	O
developing	O
the	O
Colossus	B-Device
computer	I-Device
for	O
code	O
breaking	O
at	O
Bletchley	O
Park	O
during	O
World	O
War	O
II	O
,	O
Max	O
Newman	O
was	O
committed	O
to	O
the	O
development	O
of	O
a	O
computer	O
incorporating	O
both	O
Alan	O
Turing	O
's	O
mathematical	O
concepts	O
and	O
the	O
stored-program	O
concept	O
that	O
had	O
been	O
described	O
by	O
John	O
von	O
Neumann	O
.	O
</s>
<s>
In	O
1945	O
,	O
he	O
was	O
appointed	O
to	O
the	O
Fielden	O
Chair	O
of	O
Pure	O
Mathematics	O
at	O
Manchester	O
University	O
;	O
he	O
took	O
his	O
Colossus-project	O
colleagues	O
Jack	O
Good	O
and	O
David	O
Rees	O
to	O
Manchester	O
with	O
him	O
,	O
and	O
there	O
they	O
recruited	O
F	O
.	O
C	O
.	O
Williams	O
to	O
be	O
the	O
"	O
circuit	O
man	O
"	O
for	O
a	O
new	O
computer	O
project	O
for	O
which	O
he	O
had	O
secured	O
funding	O
from	O
the	O
Royal	O
Society	O
.	O
</s>
<s>
By	O
the	O
autumn	O
of	O
1947	O
the	O
pair	O
had	O
increased	O
the	O
storage	O
capacity	O
of	O
the	O
Williams	B-General_Concept
tube	I-General_Concept
from	O
one	O
bit	O
to	O
2	O
,	O
048	O
,	O
arranged	O
in	O
a	O
64	O
by	O
32-bit	O
array	O
,	O
and	O
demonstrated	O
that	O
it	O
was	O
able	O
to	O
store	O
those	O
bits	O
for	O
four	O
hours	O
.	O
</s>
<s>
Jack	O
Copeland	O
explains	O
that	O
Kilburn	O
's	O
first	O
(	O
pre-Baby	O
)	O
accumulator-free	O
(	O
decentralized	O
,	O
in	O
Jack	O
Good	O
's	O
nomenclature	O
)	O
design	O
was	O
based	O
on	O
inputs	O
from	O
Turing	O
,	O
but	O
that	O
he	O
later	O
switched	O
to	O
an	O
accumulator-based	O
(	O
centralized	O
)	O
machine	O
of	O
the	O
sort	O
advocated	O
by	O
von	O
Neumann	O
,	O
as	O
written	O
up	O
and	O
taught	O
to	O
him	O
by	O
Jack	O
Good	O
and	O
Max	O
Newman	O
.	O
</s>
<s>
The	O
Baby	O
's	O
seven	O
operation	B-Language
instruction	B-General_Concept
set	I-General_Concept
was	O
approximately	O
a	O
subset	O
of	O
the	O
twelve	O
operation	B-Language
instruction	B-General_Concept
set	I-General_Concept
proposed	O
in	O
1947	O
by	O
Jack	O
Good	O
,	O
in	O
the	O
first	O
known	O
document	O
to	O
use	O
the	O
term	O
"	O
Baby	O
"	O
for	O
this	O
machine	O
.	O
</s>
<s>
Although	O
Newman	O
played	O
no	O
engineering	O
role	O
in	O
the	O
development	O
of	O
the	O
Baby	O
,	O
or	O
any	O
of	O
the	O
subsequent	O
Manchester	B-Device
computers	I-Device
,	O
he	O
was	O
generally	O
supportive	O
and	O
enthusiastic	O
about	O
the	O
project	O
,	O
and	O
arranged	O
for	O
the	O
acquisition	O
of	O
war-surplus	O
supplies	O
for	O
its	O
construction	O
,	O
including	O
GPO	O
metal	O
racks	O
and	O
"	O
…	O
the	O
material	O
of	O
two	O
complete	O
Colossi	O
"	O
from	O
Bletchley	O
.	O
</s>
<s>
The	O
Baby	O
used	O
one	O
Williams	B-General_Concept
tube	I-General_Concept
to	O
provide	O
32	O
by	O
32-bit	O
words	O
of	O
random-access	B-Architecture
memory	I-Architecture
(	O
RAM	B-Architecture
)	O
,	O
a	O
second	O
to	O
hold	O
a	O
32-bit	O
accumulator	B-General_Concept
in	O
which	O
the	O
intermediate	O
results	O
of	O
a	O
calculation	O
could	O
be	O
stored	O
temporarily	O
,	O
and	O
a	O
third	O
to	O
hold	O
the	O
current	O
program	O
instruction	O
along	O
with	O
its	O
address	B-General_Concept
in	O
memory	B-General_Concept
.	O
</s>
<s>
Each	O
32-bit	O
word	O
of	O
RAM	B-Architecture
could	O
contain	O
either	O
a	O
program	O
instruction	O
or	O
data	O
.	O
</s>
<s>
In	O
a	O
program	O
instruction	O
,	O
bits	O
0	O
–	O
12	O
represented	O
the	O
memory	B-General_Concept
address	I-General_Concept
of	O
the	O
operand	O
to	O
be	O
used	O
,	O
and	O
bits	O
13	O
–	O
15	O
specified	O
the	O
operation	B-Language
to	O
be	O
executed	O
,	O
such	O
as	O
storing	O
a	O
number	O
in	O
memory	B-General_Concept
;	O
the	O
remaining	O
16bits	O
were	O
unused	O
.	O
</s>
<s>
The	O
Baby	O
's	O
0-operand	O
instruction	O
set|single	O
operand	O
architecture	O
meant	O
that	O
the	O
second	O
operand	O
of	O
any	O
operation	B-Language
was	O
implicit	O
:	O
the	O
accumulator	B-General_Concept
or	O
the	O
program	O
counter	O
(	O
instruction	O
address	B-General_Concept
)	O
;	O
program	O
instructions	O
specified	O
only	O
the	O
address	B-General_Concept
of	O
the	O
data	O
in	O
memory	B-General_Concept
.	O
</s>
<s>
A	O
word	O
in	O
the	O
computer	O
's	O
memory	B-General_Concept
could	O
be	O
read	O
,	O
written	O
,	O
or	O
refreshed	O
,	O
in	O
360microseconds	O
.	O
</s>
<s>
An	O
instruction	O
took	O
four	O
times	O
as	O
long	O
to	O
execute	O
as	O
accessing	O
a	O
word	O
from	O
memory	B-General_Concept
,	O
giving	O
an	O
instruction	O
execution	O
rate	O
of	O
about	O
700	O
per	O
second	O
.	O
</s>
<s>
The	O
Baby	O
represented	O
negative	O
numbers	O
using	O
two	B-General_Concept
's	I-General_Concept
complement	I-General_Concept
,	O
as	O
most	O
computers	O
still	O
do	O
.	O
</s>
<s>
The	O
Baby	O
's	O
instruction	O
format	O
had	O
a	O
three-bit	O
operation	B-Language
code	I-Language
field	O
,	O
which	O
allowed	O
a	O
maximum	O
of	O
eight	O
(	O
23	O
)	O
different	O
instructions	O
.	O
</s>
<s>
Programs	O
were	O
entered	O
in	O
binary	O
form	O
by	O
stepping	O
through	O
each	O
word	O
of	O
memory	B-General_Concept
in	O
turn	O
,	O
and	O
using	O
a	O
set	O
of	O
32buttons	O
and	O
switches	O
known	O
as	O
the	O
input	O
device	O
to	O
set	O
the	O
value	O
of	O
each	O
bit	O
of	O
each	O
word	O
to	O
either	O
0	O
or	O
1	O
.	O
</s>
<s>
The	O
first	O
version	O
was	O
operational	O
by	O
April	O
1949	O
,	O
and	O
it	O
in	O
turn	O
led	O
directly	O
to	O
the	O
development	O
of	O
the	O
Ferranti	B-Device
Mark	I-Device
1	I-Device
,	O
the	O
world	O
's	O
first	O
commercially	O
available	O
general-purpose	O
computer	O
.	O
</s>
<s>
Demonstrations	O
of	O
the	O
machine	O
in	O
operation	B-Language
are	O
held	O
regularly	O
at	O
the	O
museum	O
.	O
</s>
