EDSAC - A Cultural Shift in Computing

Uploaded by computingheritage on May 6, 2013


JOYCE WHEELER: We realized that things were much more
advanced, nowhere else had these facilities at the time.
DR. DAVID HARTLEY: The EDSAC was responsible if you like,
or supported researchers, or went as far as
getting Nobel Prizes.
JOYCE WHEELER: Researchers found that it was possible to
solve problems quite beyond the expectations at the time.
DR. DAVID HARTLEY: EDSAC was a general purpose
stored program machine.
And that's very fundamental because computers today
essentially do anything.

DR. ANDREW HERBERT: EDSAC was built in what at the time was
called the mathematical laboratory of Cambridge
DR. DAVID HARTLEY: The building was the anatomy
It's famous for the fact that the only elevator that it had
in it was for horizontal people rather
then vertical people.
JOYCE WHEELER: People looking for the laboratory would be
told to look for the green door which was the only
obvious door along that street.
DR. DAVID HARTLEY: It was set up to provide assistance to
people in other departments to help them do their research.
DR. ANDREW HERBERT: The EDSAC project was led by Maurice
Wilkes who was head of the mathematical laboratory.
JOYCE WHEELER: Maurice Wilkes was very formal, he always
called me Miss Blackler.
PROFESSOR ANDY HOPPER: He was quite intense in a way.
He was intellectually very determined.
Maurice's mission was to change the world.
DR. DAVID HARTLEY: Now in those days all they had was
what we called hand calculators, little machines
like this, where you turn the handle, and it did the sums.
JOYCE WHEELER: I was looking at the structure of stars and
it was very difficult to be accurate with a large
DR. DAVID HARTLEY: Maurice really wanted to do something
for all those researchers who were sort of stuck
away turning handles.

JOYCE WHEELER: Maurice had heard about machines being
built in the States.
They were electronic, therefore you knew that you
could build a large machine, and make it work.
DR. DAVID HARTLEY: He came back from the states on the
Queen Mary and while on the Queen Mary he said to himself,
I now know how to build a computer, and
sketched out the design.
And when he got back to Cambridge he said, right,
fellas we're going to build it.
JOYCE WHEELER: the core team consisted of Maurice Wilkes
with his engineer Bill Renwick.
DR. DAVID HARTLEY: Bill was the guy who really built it
with his hands, I think, together with the technicians.
Then of course with the research students, the most
famous of which is David Wheeler.
JOYCE WHEELER: When I first met him I was so impressed by
his intelligence and ability to write a program.
DR. ANDREW HERBERT: He invented the concept of a
The EDSAC Subroutine library was used by programmers to
write their programs to save them effort.
DR. DAVID HARTLEY: It's all part of why EDSAC was
important because it made programming easier.
Wilkes' memoirs say that suddenly it started to work,
that they were taking by surprise.
It must have taken some time to suddenly click in.
And it did on the 6th of May, 1949, it suddenly worked.
JOYCE WHEELER: This is the booklet that you needed in
order to learn to use EDSAC 1.
And I remember taking it to the library and working
through it in a day.
DR. DAVID HARTLEY: The first thing you had to do is you get
the student, or user, or researcher to decide what
problem they want to solve, and to write a program.
Sit down, write down the instructions
to go into the computer.
JOYCE WHEELER: All the programs were punched on to
paper tape.
And during the day there were operators employed.
MARGARET MARRS: My job was the Senior
Computer Operator on EDSAC.
We would take these jobs one by one and
run them in the computer.
And sometimes they wouldn't even read in because they were
that wrong.
DR. DAVID HARTLEY: They discovered that writing
programs was a very error prone thing, but once it was
right, you could then run it again, and again, and again,
and again very fast.
MARGARET MARRS: Monday was always a bad day for computers
because they'd been turned off at the weekend.
I wouldn't go so far as to say that it wasn't worth running
programs on a Monday morning.
But I think if you wanted to nip out and do an errand, it was
probably a good time to go.
JOYCE WHEELER: The computer was available to any member of
the University.
DR. DAVID HARTLEY: Now in the old days people who built
computers were rather wary of users because
they might spoil it.
Maurice said, no come and use it.
He was very open.
JOYCE WHEELER: Those of us who were doing large projects were
allowed to run the machine in the evening and overnight.
And it was quite an achievement if you could keep
the machine running all night, and hand it over to the
engineers in the morning.
DR. DAVID HARTLEY: You have to realize that machines in those
days were extremely unreliable.
JOYCE WHEELER: One night the machine broke down
and David was there.
And so he said, let's go and see a movie.
And that's when we got close.
We were married in 1957.
DR. ANDREW HERBERT: Very little of EDSAC survives.
When the machine was finished with, they needed the space
for its successor.
And so they had to move everything out.
We've now decided to build a replica of EDSAC as a lasting
legacy to the pioneering work by Wilkes and his team.
PROFESSOR ANDY HOPPER: When Morris retired, we established
a tradition in the computer lab.
And that is to show anybody who retires the green door
behind which they worked as members of the mathematical
laboratory as it was called then.
JOYCE WHEELER: Maurice Wilkes of course, was one of the
first to be shown the door.
And all the senior people after that.
PROFESSOR ANDY HOPPER: We had a little ceremony and little
speeches were being made.
And at the right moment a couple of colleagues walked in
with this huge green door.
And said to Maurice, we're showing you the door.
DR. ANDREW HERBERT: And so we left him holding the door for
a few moments and he got a little confused.
And then the engineers came and rescued him, and carried
the door away.
PROFESSOR ANDY HOPPER: The green door is in our coffee
room and has a plaque on it, which lists the names of all
those who were shown the door.

Pioneers, and especially David Wheeler, and Maurice Wilkes
should be remembered for being particularly brilliant people
who changed the world.
JOYCE WHEELER: Those years were very productive, very
interesting, and very exciting.
MARGARET MARRS: These computers were viewed as
something special.
Nobody knew that they were going to take off and that how
valuable it would be.
DR. DAVID HARTLEY: A student course on programming and
using computers was introduced in Cambridge in 1953.
PROFESSOR ANDY HOPPER: And the very first book on the
computer programming was the book describing
how to program EDSAC.
DR. DAVID HARTLEY: You've got a smart phone now, would you
have believed 10 years ago?
But then that is the exciting thing about computing, it
surprises you all the time.