<s>
The	O
Electronic	B-Device
Delay	I-Device
Storage	I-Device
Automatic	I-Device
Calculator	I-Device
(	O
EDSAC	B-Device
)	O
was	O
an	O
early	O
British	O
computer	O
.	O
</s>
<s>
Inspired	O
by	O
John	O
von	O
Neumann	O
's	O
seminal	O
First	O
Draft	O
of	O
a	O
Report	O
on	O
the	O
EDVAC	B-Device
,	O
the	O
machine	O
was	O
constructed	O
by	O
Maurice	O
Wilkes	O
and	O
his	O
team	O
at	O
the	O
University	O
of	O
Cambridge	O
Mathematical	O
Laboratory	O
in	O
England	O
.	O
</s>
<s>
EDSAC	B-Device
was	O
the	O
second	O
electronic	O
digital	O
stored-program	O
computer	O
to	O
go	O
into	O
regular	O
service	O
.	O
</s>
<s>
Later	O
the	O
project	O
was	O
supported	O
by	O
J	O
.	O
Lyons	O
&	O
Co	O
.	O
Ltd.	O
,	O
intending	O
to	O
develop	O
a	O
commercially	O
applied	O
computer	O
and	O
succeeding	O
in	O
Lyons	O
 '	O
development	O
of	O
LEO	B-Device
I	O
,	O
based	O
on	O
the	O
EDSAC	B-Device
design	O
.	O
</s>
<s>
Work	O
on	O
EDSAC	B-Device
started	O
during	O
1947	O
,	O
and	O
it	O
ran	O
its	O
first	O
programs	O
on	O
6May	O
1949	O
,	O
when	O
it	O
calculated	O
a	O
table	O
of	O
square	O
numbers	O
and	O
a	O
list	O
of	O
prime	O
numbers	O
.	O
</s>
<s>
EDSAC	B-Device
was	O
finally	O
shut	O
down	O
on	O
11July	O
1958	O
,	O
having	O
been	O
superseded	O
by	O
EDSAC	B-Device
2	O
,	O
which	O
remained	O
in	O
use	O
until	O
1965	O
.	O
</s>
<s>
As	O
soon	O
as	O
EDSAC	B-Device
was	O
operational	O
,	O
it	O
began	O
serving	O
the	O
university	O
's	O
research	O
needs	O
.	O
</s>
<s>
It	O
used	O
mercury	B-Language
delay	O
lines	O
for	O
memory	O
and	O
derated	O
vacuum	O
tubes	O
for	O
logic	O
.	O
</s>
<s>
Initially	O
registers	O
were	O
limited	O
to	O
an	O
accumulator	B-General_Concept
and	O
a	O
multiplier	O
register	O
.	O
</s>
<s>
In	O
1953	O
,	O
David	O
Wheeler	O
,	O
returning	O
from	O
a	O
stay	O
at	O
the	O
University	O
of	O
Illinois	O
,	O
designed	O
an	O
index	B-General_Concept
register	I-General_Concept
as	O
an	O
extension	O
to	O
the	O
original	O
EDSAC	B-Device
hardware	O
.	O
</s>
<s>
The	O
EDSAC	B-Device
's	O
main	O
memory	O
consisted	O
of	O
1024	O
locations	O
,	O
though	O
only	O
512	O
locations	O
were	O
initially	O
installed	O
.	O
</s>
<s>
All	O
instruction	O
codes	O
were	O
by	O
design	O
represented	O
by	O
one	O
mnemonic	O
letter	O
,	O
so	O
that	O
the	O
Add	O
instruction	O
,	O
for	O
example	O
,	O
used	O
the	O
EDSAC	B-Device
character	O
code	O
for	O
the	O
letterA	O
.	O
</s>
<s>
Internally	O
,	O
the	O
EDSAC	B-Device
used	O
two	B-General_Concept
's	I-General_Concept
complement	I-General_Concept
binary	O
numbers	O
.	O
</s>
<s>
The	O
accumulator	B-General_Concept
could	O
hold	O
71bits	O
,	O
including	O
the	O
sign	O
,	O
allowing	O
two	O
long	O
(	O
35-bit	O
)	O
numbers	O
to	O
be	O
multiplied	O
without	O
losing	O
any	O
precision	O
.	O
</s>
<s>
There	O
was	O
no	O
division	O
instruction	O
(	O
but	O
various	O
division	O
subroutines	O
were	O
supplied	O
)	O
and	O
no	O
way	O
to	O
directly	O
load	O
a	O
number	O
into	O
the	O
accumulator	B-General_Concept
(	O
a	O
"	O
sTore	O
and	O
zero	O
accumulator	B-General_Concept
"	O
instruction	O
followed	O
by	O
an	O
"	O
Add	O
"	O
instruction	O
were	O
necessary	O
for	O
this	O
)	O
.	O
</s>
<s>
Maurice	O
Wilkes	O
discussed	O
relative	O
addressing	O
modes	O
for	O
the	O
EDSAC	B-Device
in	O
a	O
paper	O
published	O
in	O
1953	O
.	O
</s>
<s>
By	O
May	O
1949	O
,	O
the	O
initial	O
orders	O
provided	O
a	O
primitive	O
relocating	O
assembler	B-Language
taking	O
advantage	O
of	O
the	O
mnemonic	O
design	O
described	O
above	O
,	O
all	O
in	O
31	O
words	O
.	O
</s>
<s>
This	O
was	O
the	O
world	O
's	O
first	O
assembler	B-Language
,	O
and	O
arguably	O
the	O
start	O
of	O
the	O
global	O
software	O
industry	O
.	O
</s>
<s>
There	O
is	O
a	O
simulation	O
of	O
EDSAC	B-Device
available	O
and	O
a	O
full	O
description	O
of	O
the	O
initial	O
orders	O
and	O
first	O
programs	O
.	O
</s>
<s>
The	O
first	O
calculation	O
done	O
by	O
EDSAC	B-Device
was	O
a	O
square-number	O
program	O
run	O
on	O
6May	O
1949	O
.	O
</s>
<s>
Users	O
prepared	O
their	O
programs	O
by	O
punching	O
them	O
(	O
in	O
assembler	B-Language
)	O
onto	O
a	O
paper	O
tape	O
.	O
</s>
<s>
The	O
machine	O
operators	O
,	O
who	O
were	O
present	O
during	O
the	O
day	O
,	O
selected	O
the	O
next	O
tape	O
from	O
the	O
line	O
and	O
loaded	O
it	O
into	O
EDSAC	B-Device
.	O
</s>
<s>
Debuggers	O
were	O
some	O
time	O
away	O
,	O
but	O
a	O
cathode-ray	B-Device
tube	I-Device
screen	O
could	O
be	O
set	O
to	O
display	O
the	O
contents	O
of	O
a	O
particular	O
piece	O
of	O
memory	O
.	O
</s>
<s>
A	O
loudspeaker	O
was	O
connected	O
to	O
the	O
accumulator	B-General_Concept
's	O
sign	O
bit	O
;	O
experienced	O
users	O
knew	O
healthy	O
and	O
unhealthy	O
sounds	O
of	O
programs	O
,	O
particularly	O
programs	O
"	O
hung	O
"	O
in	O
a	O
loop	O
.	O
</s>
<s>
The	O
early	O
programmers	O
had	O
to	O
make	O
use	O
of	O
techniques	O
frowned	O
upon	O
today	O
—	O
in	O
particular	O
,	O
the	O
use	O
of	O
self-modifying	B-Application
code	I-Application
.	O
</s>
<s>
As	O
there	O
was	O
no	O
index	B-General_Concept
register	I-General_Concept
until	O
much	O
later	O
,	O
the	O
only	O
way	O
of	O
accessing	O
an	O
array	O
was	O
to	O
alter	O
which	O
memory	O
location	O
a	O
particular	O
instruction	O
was	O
referencing	O
.	O
</s>
<s>
David	O
Wheeler	O
,	O
who	O
earned	O
the	O
world	B-Architecture
's	I-Architecture
first	I-Architecture
Computer	I-Architecture
Science	O
PhD	O
working	O
on	O
the	O
project	O
,	O
is	O
credited	O
with	O
inventing	O
the	O
concept	O
of	O
a	O
subroutine	O
.	O
</s>
<s>
Users	O
wrote	O
programs	O
that	O
called	O
a	O
routine	O
by	O
jumping	O
to	O
the	O
start	O
of	O
the	O
subroutine	O
with	O
the	O
return	B-Language
address	I-Language
(	O
i.e.	O
</s>
<s>
the	O
location-plus-one	O
of	O
the	O
jump	O
itself	O
)	O
in	O
the	O
accumulator	B-General_Concept
(	O
a	O
Wheeler	O
Jump	O
)	O
.	O
</s>
<s>
By	O
convention	O
the	O
subroutine	O
expected	O
this	O
,	O
and	O
the	O
first	O
thing	O
it	O
did	O
was	O
to	O
modify	O
its	O
concluding	O
jump	O
instruction	O
to	O
that	O
return	B-Language
address	I-Language
.	O
</s>
<s>
(	O
However	O
,	O
Turing	O
discussed	O
subroutines	O
in	O
a	O
paper	O
of	O
1945	O
on	O
design	O
proposals	O
for	O
the	O
NPL	O
ACE	B-Device
,	O
going	O
so	O
far	O
as	O
to	O
invent	O
the	O
concept	O
of	O
a	O
return-address	O
stack	O
,	O
which	O
would	O
have	O
allowed	O
recursion	O
.	O
)	O
</s>
<s>
The	O
lack	O
of	O
an	O
index	B-General_Concept
register	I-General_Concept
also	O
posed	O
a	O
problem	O
to	O
the	O
writer	O
of	O
a	O
subroutine	O
in	O
that	O
they	O
could	O
not	O
know	O
in	O
advance	O
where	O
in	O
memory	O
the	O
subroutine	O
would	O
be	O
loaded	O
,	O
and	O
therefore	O
they	O
could	O
not	O
know	O
how	O
to	O
address	O
any	O
regions	O
of	O
the	O
code	O
that	O
were	O
used	O
for	O
storage	O
of	O
data	O
(	O
so-called	O
"	O
pseudo-orders	O
"	O
)	O
.	O
</s>
<s>
EDSAC	B-Device
's	O
programmers	O
used	O
special	O
techniques	O
to	O
make	O
best	O
use	O
of	O
the	O
limited	O
available	O
memory	O
.	O
</s>
<s>
By	O
1951	O
,	O
87	O
subroutines	O
in	O
the	O
following	O
categories	O
were	O
available	O
for	O
general	O
use	O
:	O
floating-point	B-Algorithm
arithmetic	I-Algorithm
;	O
arithmetic	O
operations	O
on	O
complex	O
numbers	O
;	O
checking	O
;	O
division	O
;	O
exponentiation	O
;	O
routines	O
relating	O
to	O
functions	O
;	O
differential	O
equations	O
;	O
special	O
functions	O
;	O
power	O
series	O
;	O
logarithms	O
;	O
miscellaneous	O
;	O
print	O
and	O
layout	O
;	O
quadrature	B-Algorithm
;	O
read	O
(	O
input	O
)	O
;	O
nth	O
root	O
;	O
trigonometric	O
functions	O
;	O
counting	O
operations	O
(	O
simulating	O
repeat	O
until	O
loops	O
,	O
while	O
loops	O
and	O
for	B-Language
loops	I-Language
)	O
;	O
vectors	O
;	O
and	O
matrices	B-Architecture
.	O
</s>
<s>
The	O
first	O
assembly	B-Language
language	I-Language
appeared	O
for	O
the	O
EDSAC	B-Device
,	O
and	O
inspired	O
several	O
other	O
assembly	B-Language
languages	I-Language
:	O
</s>
<s>
EDSAC	B-Device
was	O
designed	O
specifically	O
to	O
form	O
part	O
of	O
the	O
Mathematical	O
Laboratory	O
's	O
support	O
service	O
for	O
calculation	O
.	O
</s>
<s>
Wilkes	O
and	O
Wheeler	O
had	O
used	O
EDSAC	B-Device
to	O
solve	O
a	O
differential	O
equation	O
relating	O
to	O
gene	O
frequencies	O
for	O
him	O
.	O
</s>
<s>
The	O
winners	O
of	O
three	O
Nobel	O
Prizes	O
John	O
Kendrew	O
and	O
Max	O
Perutz	O
(	O
Chemistry	O
,	O
1962	O
)	O
,	O
Andrew	O
Huxley	O
(	O
Medicine	O
,	O
1963	O
)	O
and	O
Martin	O
Ryle	O
(	O
Physics	O
,	O
1974	O
)	O
benefitted	O
from	O
EDSAC	B-Device
's	O
revolutionary	O
computing	O
power	O
.	O
</s>
<s>
In	O
their	O
acceptance	O
prize	O
speeches	O
,	O
each	O
acknowledged	O
the	O
role	O
that	O
EDSAC	B-Device
had	O
played	O
in	O
their	O
research	O
.	O
</s>
<s>
In	O
the	O
early	O
1960s	O
Peter	O
Swinnerton-Dyer	O
used	O
the	O
EDSAC	B-Device
computer	O
to	O
calculate	O
the	O
number	O
of	O
points	O
modulo	O
p	O
(	O
denoted	O
by	O
Np	O
)	O
for	O
a	O
large	O
number	O
of	O
primes	O
p	O
on	O
elliptic	O
curves	O
whose	O
rank	O
was	O
known	O
.	O
</s>
<s>
In	O
1952	O
,	O
Sandy	O
Douglas	O
developed	O
OXO	B-Application
,	O
a	O
version	O
of	O
noughts	B-Application
and	I-Application
crosses	I-Application
(	O
tic-tac-toe	O
)	O
for	O
the	O
EDSAC	B-Device
,	O
with	O
graphical	O
output	O
to	O
a	O
VCR97	O
6	O
"	O
cathode-ray	B-Device
tube	I-Device
.	O
</s>
<s>
This	O
may	O
well	O
have	O
been	O
the	O
world	O
's	O
first	B-Application
video	I-Application
game	I-Application
.	O
</s>
<s>
The	O
Stanley	O
Gill	O
game	O
was	O
controlled	O
via	O
the	O
lightbeam	O
of	O
the	O
EDSAC	B-Device
's	O
paper-tape	O
reader	O
.	O
</s>
<s>
EDSAC	B-Device
's	O
successor	O
,	O
EDSAC	B-Device
2	I-Device
,	O
was	O
commissioned	O
in	O
1958	O
.	O
</s>
<s>
In	O
1961	O
,	O
an	O
EDSAC	B-Device
2	I-Device
version	O
of	O
Autocode	B-Language
,	O
an	O
ALGOL-like	B-Language
high-level	O
programming	O
language	O
for	O
scientists	O
and	O
engineers	O
,	O
was	O
developed	O
by	O
David	O
Hartley	O
.	O
</s>
<s>
In	O
the	O
mid-1960s	O
,	O
a	O
successor	O
to	O
the	O
EDSAC	B-Device
2	I-Device
was	O
planned	O
,	O
but	O
the	O
move	O
was	O
instead	O
made	O
to	O
the	O
Titan	B-Device
,	O
a	O
prototype	O
Atlas2	O
developed	O
from	O
the	O
Atlas	B-Device
Computer	I-Device
of	O
the	O
University	O
of	O
Manchester	O
,	O
Ferranti	O
,	O
and	O
Plessey	O
.	O
</s>
<s>
On	O
13	O
January	O
2011	O
,	O
the	O
Computer	O
Conservation	O
Society	O
announced	O
that	O
it	O
planned	O
to	O
build	O
a	O
working	O
replica	O
of	O
EDSAC	B-Device
,	O
at	O
the	O
National	O
Museum	O
of	O
Computing	O
(	O
TNMoC	O
)	O
in	O
Bletchley	O
Park	O
supervised	O
by	O
Andrew	O
Herbert	O
,	O
who	O
studied	O
under	O
Maurice	O
Wilkes	O
.	O
</s>
<s>
In	O
2016	O
,	O
two	O
original	O
EDSAC	B-Device
operators	O
,	O
Margaret	O
Marrs	O
and	O
Joyce	O
Wheeler	O
,	O
visited	O
the	O
museum	O
to	O
assist	O
the	O
project	O
.	O
</s>
