<s>
The	O
Manchester	B-Device
Mark	I-Device
1	I-Device
was	O
one	O
of	O
the	O
earliest	O
stored-program	O
computers	O
,	O
developed	O
at	O
the	O
Victoria	O
University	O
of	O
Manchester	O
,	O
England	O
from	O
the	O
Manchester	B-Device
Baby	I-Device
(	O
operational	O
in	O
June	O
1948	O
)	O
.	O
</s>
<s>
Development	O
ceased	O
at	O
the	O
end	O
of	O
1949	O
,	O
and	O
the	O
machine	O
was	O
scrapped	O
towards	O
the	O
end	O
of	O
1950	O
,	O
replaced	O
in	O
February	O
1951	O
by	O
a	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
electronic	O
computer	O
.	O
</s>
<s>
The	O
computer	O
is	O
especially	O
historically	O
significant	O
because	O
of	O
its	O
pioneering	O
inclusion	O
of	O
index	B-General_Concept
registers	I-General_Concept
,	O
an	O
innovation	O
which	O
made	O
it	O
easier	O
for	O
a	O
program	O
to	O
read	O
sequentially	O
through	O
an	O
array	O
of	O
words	O
in	O
memory	O
.	O
</s>
<s>
Thirty-four	O
patents	O
resulted	O
from	O
the	O
machine	O
's	O
development	O
,	O
and	O
many	O
of	O
the	O
ideas	O
behind	O
its	O
design	O
were	O
incorporated	O
in	O
subsequent	O
commercial	O
products	O
such	O
as	O
the	O
and	O
702	B-Device
as	O
well	O
as	O
the	O
Ferranti	B-Device
Mark	I-Device
1	I-Device
.	O
</s>
<s>
In	O
1951	O
,	O
they	O
started	O
development	O
work	O
on	O
Meg	O
,	O
the	O
Mark1	O
's	O
successor	O
,	O
which	O
would	O
include	O
a	O
floating	B-General_Concept
point	I-General_Concept
unit	I-General_Concept
.	O
</s>
<s>
During	O
the	O
1940s	O
,	O
Turing	O
and	O
others	O
such	O
as	O
Konrad	O
Zuse	O
developed	O
the	O
idea	O
of	O
using	O
the	O
computer	O
's	O
own	O
memory	O
to	O
hold	O
both	O
the	O
program	O
and	O
data	O
,	O
instead	O
of	O
tape	O
,	O
but	O
it	O
was	O
mathematician	O
John	O
von	O
Neumann	O
who	O
became	O
widely	O
credited	O
with	O
defining	O
that	O
stored-program	O
computer	O
architecture	O
,	O
on	O
which	O
the	O
Manchester	B-Device
Mark	I-Device
1	I-Device
was	O
based	O
.	O
</s>
<s>
The	O
University	O
of	O
Manchester	O
's	O
Baby	B-Device
,	O
the	O
world	O
's	O
first	O
electronic	O
stored-program	O
computer	O
,	O
had	O
successfully	O
demonstrated	O
the	O
practicality	O
of	O
the	O
stored-program	O
approach	O
and	O
of	O
the	O
Williams	B-General_Concept
tube	I-General_Concept
,	O
an	O
early	O
form	O
of	O
computer	O
memory	O
based	O
on	O
a	O
standard	O
cathode-ray	B-Device
tube	I-Device
(	O
CRT	B-Device
)	O
,	O
by	O
running	O
its	O
first	O
program	O
on	O
21	O
June	O
1948	O
.	O
</s>
<s>
Early	O
electronic	O
computers	O
were	O
generally	O
programmed	O
by	O
being	O
rewired	O
,	O
or	O
via	O
plugs	B-Protocol
and	I-Protocol
patch	I-Protocol
panels	I-Protocol
;	O
there	O
was	O
no	O
separate	O
program	O
stored	O
in	O
memory	O
,	O
as	O
in	O
a	O
modern	O
computer	O
.	O
</s>
<s>
It	O
could	O
take	O
several	O
days	O
to	O
reprogram	O
ENIAC	B-Device
,	O
for	O
instance	O
.	O
</s>
<s>
Stored-program	O
computers	O
were	O
also	O
being	O
developed	O
by	O
other	O
researchers	O
,	O
notably	O
the	O
National	O
Physical	O
Laboratory	O
's	O
Pilot	B-Device
ACE	I-Device
,	O
Cambridge	O
University	O
's	O
EDSAC	B-Device
,	O
and	O
the	O
US	O
Army	O
's	O
EDVAC	B-Device
.	O
</s>
<s>
The	O
Baby	B-Device
and	O
the	O
Mark	O
1	O
differed	O
primarily	O
in	O
their	O
use	O
of	O
Williams	B-General_Concept
tubes	I-General_Concept
as	O
memory	O
devices	O
,	O
instead	O
of	O
mercury	B-Device
delay	O
lines	O
.	O
</s>
<s>
From	O
about	O
August	O
1948	O
,	O
the	O
Baby	B-Device
was	O
intensively	O
developed	O
as	O
a	O
prototype	O
for	O
the	O
Manchester	B-Device
Mark	I-Device
1	I-Device
,	O
initially	O
with	O
the	O
aim	O
of	O
providing	O
the	O
university	O
with	O
a	O
more	O
realistic	O
computing	O
facility	O
.	O
</s>
<s>
Lockspeiser	O
was	O
so	O
impressed	O
by	O
what	O
he	O
saw	O
that	O
he	O
immediately	O
initiated	O
a	O
government	O
contract	O
with	O
the	O
local	O
firm	O
of	O
Ferranti	O
to	O
make	O
a	O
commercial	O
version	O
of	O
the	O
machine	O
,	O
the	O
Ferranti	B-Device
Mark	I-Device
1	I-Device
.	O
</s>
<s>
The	O
Baby	B-Device
had	O
been	O
designed	O
by	O
the	O
team	O
of	O
Frederic	O
C	O
.	O
Williams	O
,	O
Tom	O
Kilburn	O
and	O
Geoff	O
Tootill	O
.	O
</s>
<s>
The	O
project	O
soon	O
had	O
the	O
dual	O
purpose	O
of	O
supplying	O
Ferranti	O
with	O
a	O
working	O
design	O
on	O
which	O
they	O
could	O
base	O
a	O
commercial	O
machine	O
,	O
the	O
Ferranti	B-Device
Mark	I-Device
1	I-Device
,	O
and	O
of	O
building	O
a	O
computer	O
that	O
would	O
allow	O
researchers	O
to	O
gain	O
experience	O
of	O
how	O
such	O
a	O
machine	O
could	O
be	O
used	O
in	O
practice	O
.	O
</s>
<s>
The	O
first	O
of	O
the	O
two	O
versions	O
of	O
the	O
Manchester	B-Device
Mark	I-Device
1	I-Device
–	O
known	O
as	O
the	O
Intermediary	O
Version	O
–	O
was	O
operational	O
by	O
April	O
1949	O
.	O
</s>
<s>
To	O
increase	O
reliability	O
,	O
purpose-built	O
CRTs	O
made	O
by	O
GEC	O
were	O
used	O
in	O
the	O
machine	O
instead	O
of	O
the	O
standard	O
devices	O
used	O
in	O
the	O
Baby	B-Device
.	O
</s>
<s>
The	O
Baby	B-Device
's	O
32-bit	O
word	O
length	O
was	O
increased	O
to	O
40	O
bits	O
.	O
</s>
<s>
The	O
main	O
store	O
initially	O
consisted	O
of	O
two	O
double-density	O
Williams	B-General_Concept
tubes	I-General_Concept
,	O
each	O
holding	O
two	O
arrays	O
of	O
32	O
x	O
40-bit	O
words	O
–	O
known	O
as	O
pages	B-General_Concept
–	O
backed	O
up	O
by	O
a	O
magnetic	O
drum	O
capable	O
of	O
storing	O
an	O
additional	O
32	O
pages	B-General_Concept
.	O
</s>
<s>
The	O
capacity	O
was	O
increased	O
in	O
the	O
Final	O
Specification	O
version	O
to	O
eight	O
pages	B-General_Concept
of	O
main	O
store	O
on	O
four	O
Williams	B-General_Concept
tubes	I-General_Concept
and	O
128	O
magnetic	O
drum	O
pages	B-General_Concept
of	O
backing	O
store	O
.	O
</s>
<s>
One	O
revolution	O
of	O
the	O
drum	O
took	O
30milliseconds	O
,	O
during	O
which	O
time	O
both	O
pages	B-General_Concept
could	O
be	O
transferred	O
to	O
the	O
CRT	B-Device
main	O
memory	O
,	O
although	O
the	O
actual	O
data	O
transfer	O
time	O
depended	O
on	O
the	O
latency	O
,	O
the	O
time	O
it	O
took	O
for	O
a	O
page	O
to	O
arrive	O
under	O
the	O
read/write	O
head	O
.	O
</s>
<s>
Writing	O
pages	B-General_Concept
to	O
the	O
drum	O
took	O
about	O
twice	O
as	O
long	O
as	O
reading	O
.	O
</s>
<s>
Data	O
was	O
recorded	O
onto	O
the	O
drum	O
using	O
a	O
phase	B-Device
modulation	I-Device
technique	O
still	O
known	O
today	O
as	O
Manchester	B-Protocol
coding	I-Protocol
.	O
</s>
<s>
The	O
machine	O
's	O
instruction	B-General_Concept
set	I-General_Concept
was	O
increased	O
from	O
the	O
7	O
of	O
the	O
Baby	B-Device
to	O
26	O
initially	O
,	O
including	O
multiplication	O
done	O
in	O
hardware	O
.	O
</s>
<s>
Ten	O
bits	O
of	O
each	O
word	O
were	O
allocated	O
to	O
hold	O
the	O
instruction	B-General_Concept
code	I-General_Concept
.	O
</s>
<s>
The	O
machine	O
's	O
most	O
significant	O
innovation	O
is	O
generally	O
considered	O
to	O
be	O
its	O
incorporation	O
of	O
index	B-General_Concept
registers	I-General_Concept
,	O
commonplace	O
on	O
modern	O
computers	O
.	O
</s>
<s>
The	O
Baby	B-Device
had	O
included	O
two	O
registers	O
,	O
implemented	O
as	O
Williams	B-General_Concept
tubes	I-General_Concept
:	O
the	O
accumulator	B-General_Concept
(	O
A	O
)	O
and	O
the	O
program	B-General_Concept
counter	I-General_Concept
(	O
C	O
)	O
.	O
</s>
<s>
As	O
A	O
and	O
C	O
had	O
already	O
been	O
assigned	O
,	O
the	O
tube	O
holding	O
the	O
two	O
index	B-General_Concept
registers	I-General_Concept
,	O
originally	O
known	O
as	O
B-lines	O
,	O
was	O
given	O
the	O
name	O
B	O
.	O
</s>
<s>
Of	O
the	O
20	O
bits	O
allocated	O
for	O
each	O
program	O
instruction	O
,	O
10	O
were	O
used	O
to	O
hold	O
the	O
instruction	B-General_Concept
code	I-General_Concept
,	O
which	O
allowed	O
for	O
1,024	O
(	O
210	O
)	O
different	O
instructions	O
.	O
</s>
<s>
The	O
machine	O
had	O
26	O
initially	O
,	O
increasing	O
to	O
30	O
when	O
the	O
function	O
codes	O
to	O
programmatically	O
control	O
the	O
data	O
transfer	O
between	O
the	O
magnetic	O
drum	O
and	O
the	O
cathode-ray	B-Device
tube	I-Device
(	O
CRT	B-Device
)	O
main	O
store	O
were	O
added	O
.	O
</s>
<s>
On	O
the	O
Intermediary	O
Version	O
programs	O
were	O
input	O
by	O
key	O
switches	O
,	O
and	O
the	O
output	O
was	O
displayed	O
as	O
a	O
series	O
of	O
dots	O
and	O
dashes	O
on	O
a	O
cathode-ray	B-Device
tube	I-Device
known	O
as	O
the	O
output	O
device	O
,	O
just	O
as	O
on	O
the	O
Baby	B-Device
from	O
which	O
the	O
Mark	O
1	O
had	O
been	O
developed	O
.	O
</s>
<s>
There	O
was	O
no	O
assembly	B-Language
language	I-Language
defined	O
for	O
the	O
Mark	O
1	O
.	O
</s>
<s>
The	O
Mark	O
1	O
had	O
no	O
system	O
of	O
hardware	B-Application
interrupts	I-Application
;	O
the	O
program	O
continued	O
after	O
a	O
read	O
or	O
write	O
operation	O
had	O
been	O
initiated	O
until	O
another	O
input/output	O
instruction	O
was	O
encountered	O
,	O
at	O
which	O
point	O
the	O
machine	O
waited	O
for	O
the	O
first	O
to	O
complete	O
.	O
</s>
<s>
The	O
Mark	O
1	O
had	O
no	O
operating	B-General_Concept
system	I-General_Concept
;	O
its	O
only	O
system	O
software	O
was	O
a	O
few	O
basic	O
routines	O
for	O
input	O
and	O
output	O
.	O
</s>
<s>
As	O
in	O
the	O
Baby	B-Device
from	O
which	O
it	O
was	O
developed	O
,	O
and	O
in	O
contrast	O
to	O
the	O
established	O
mathematical	O
convention	O
,	O
the	O
machine	O
's	O
storage	O
was	O
arranged	O
with	O
the	O
least	O
significant	O
digits	O
to	O
the	O
left	O
;	O
thus	O
a	O
one	O
was	O
represented	O
in	O
five	O
bits	O
as	O
"	O
10000	O
"	O
,	O
rather	O
than	O
the	O
more	O
conventional	O
"	O
00001	O
"	O
.	O
</s>
<s>
Negative	O
numbers	O
were	O
represented	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
today	O
.	O
</s>
<s>
The	O
Manchester	B-Device
Mark	I-Device
1	I-Device
continued	O
to	O
do	O
useful	O
mathematical	O
work	O
until	O
1950	O
,	O
including	O
an	O
investigation	O
of	O
the	O
Riemann	O
hypothesis	O
and	O
calculations	O
in	O
optics	B-Algorithm
.	O
</s>
<s>
Tootill	O
was	O
temporarily	O
transferred	O
from	O
the	O
University	O
of	O
Manchester	O
to	O
Ferranti	O
in	O
August	O
1949	O
,	O
to	O
continue	O
work	O
on	O
the	O
Ferranti	B-Device
Mark	I-Device
1	I-Device
's	O
design	O
,	O
and	O
spent	O
four	O
months	O
working	O
with	O
the	O
company	O
.	O
</s>
<s>
The	O
Manchester	B-Device
Mark	I-Device
1	I-Device
was	O
dismantled	O
and	O
scrapped	O
in	O
August	O
1950	O
,	O
replaced	O
a	O
few	O
months	O
later	O
by	O
the	O
first	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>
Between	O
1946	O
and	O
1949	O
,	O
the	O
average	O
size	O
of	O
the	O
design	O
team	O
working	O
on	O
the	O
Mark	O
1	O
and	O
its	O
predecessor	O
,	O
the	O
Baby	B-Device
,	O
had	O
been	O
about	O
four	O
people	O
.	O
</s>
<s>
The	O
company	O
subsequently	O
licensed	O
several	O
of	O
the	O
patented	O
ideas	O
developed	O
for	O
the	O
machine	O
,	O
including	O
the	O
Williams	B-General_Concept
tube	I-General_Concept
,	O
in	O
the	O
design	O
of	O
its	O
own	O
701	B-Device
and	O
702	B-Device
computers	O
.	O
</s>
<s>
The	O
most	O
significant	O
design	O
legacy	O
of	O
the	O
Manchester	B-Device
Mark	I-Device
1	I-Device
was	O
perhaps	O
its	O
incorporation	O
of	O
index	B-General_Concept
registers	I-General_Concept
,	O
the	O
patent	O
for	O
which	O
was	O
taken	O
out	O
in	O
the	O
names	O
of	O
Williams	O
,	O
Kilburn	O
,	O
Tootill	O
,	O
and	O
Newman	O
.	O
</s>
<s>
Kilburn	O
and	O
Williams	O
concluded	O
that	O
computers	O
would	O
be	O
used	O
more	O
in	O
scientific	O
roles	O
than	O
pure	O
maths	O
,	O
and	O
decided	O
to	O
develop	O
a	O
new	O
machine	O
that	O
would	O
include	O
a	O
floating	B-General_Concept
point	I-General_Concept
unit	I-General_Concept
.	O
</s>
<s>
Ferranti	O
produced	O
a	O
version	O
of	O
Meg	O
with	O
the	O
Williams	B-General_Concept
tubes	I-General_Concept
replaced	O
by	O
the	O
more	O
reliable	O
core	B-General_Concept
memory	I-General_Concept
,	O
marketed	O
as	O
the	B-Device
Ferranti	I-Device
Mercury	I-Device
.	O
</s>
<s>
The	O
successful	O
operation	O
of	O
the	O
Manchester	B-Device
Mark	I-Device
1	I-Device
and	O
its	O
predecessor	O
,	O
the	O
Baby	B-Device
,	O
was	O
widely	O
reported	O
in	O
the	O
British	O
press	O
,	O
which	O
used	O
the	O
phrase	O
"	O
electronic	O
brain	O
"	O
to	O
describe	O
the	O
machines	O
.	O
</s>
