EDSAC – A Cultural Shift in Computing
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EDSAC – A Cultural Shift in Computing

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 University. DR. DAVID HARTLEY: The building
was the anatomy department. 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 calculation. 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 subroutine. 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.


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