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Machines and Men's Minds:
Manchester, 1948-1950

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The World's First Working Universal Turing Machine

The story moves to Manchester, heart of the commercial and industrial North of England.

But the story of the Manchester computer begins at Bletchley Park in 1944. There, the Cambridge mathematician M. H. A. Newman had determined the function and organised the use of the Colossus electronic machine (see this Scrapbook Page) for breaking the top-level German strategic messages. In 1945 he became Professor of Pure Mathematics at Manchester University, and had ambitious plans to build up a powerful department there. He hoped to take advantage of what had been achieved at Bletchley Park, and turn it to peaceful scientific research.

His ally was the physicist Patrick Blackett, Nobel prize winner in 1948 for the experimental discovery of the positron, the pioneer of Operational Research in wartime, and a highly influential figure with the Labour government of 1945-1950.

The soft part

In 1935 it was Newman who had introduced Turing to the problem which led to the Turing machine (see this Scrapbook page), and Newman was the first person ever to read of Turing's universal machine in 1936. Now the war had proved the reliability and speed of electronic digital technology. Max Newman was a pure mathematician, but the war had given him, like Turing, a vision of what an electronic computer could do; and he was fully aware of the power of Turing's universal machine concept.

Unlike Turing, however, he had no interest in getting involved personally in electronic engineering.

Newman acted swiftly. In February 1946 Newman wrote to von Neumann that he was

hoping to embark on a computing machine section here, having got very interested in electronic devices of this kind during the last two or three years. By about 18 months ago [i.e. soon after D-Day, and a year before von Neumann's EDVAC report] I had decided to try my hand at starting up a machine unit when I got out. It was indeed one of my reasons for coming to Manchester that the set-up here is favourable in several ways... I am of course in close touch with Turing...

This letter is in the von Neumann papers held in the Library of Congress, where I found it in 1979.

Note that at this date, Turing had not even had his ACE proposal accepted by the National Physical Laboratory; these were very early days.

Newman's intention was that the machine would be used for pure mathematical work in algebra and topology, for instance the Four Colour Theorem. The Royal Society approved the project and allocated a grant to Newman for salaries and construction totalling 35,000 (about a million pounds in real terms now), with the comment that 'Newman himself, because of his mathematical background and wartime experience, is particularly well qualified for directing this project.'

At that stage, early 1946, Newman expected that that the American Iconoscope would become available as the storage system. But it didn't work.

The hard part

Meanwhile at the radar establishment, TRE, the top electronic engineers had found themselves suddenly out of a job in August 1945. F. C. Williams looked around for a leading-edge project. He soon heard that the possibility of building electronic computers was in the air and that creating a storage system was the main technological bottle-neck.

He had a bright idea for storing digits as bright spots on a screen. The Williams tube converted the cathode-ray-tube into a viable storage medium for digital information.

In November 1946, Williams was appointed to the chair of electrical engineering at Manchester.

Newman's idea was that it would be advantageous to exploit Williams' work on cathode-ray-tube storage, even if, as it then appeared likely, an on-site development would take longer than the Americans. Newman had no rigid ideas about hardware, and simply wanted a computer built by the most effective means possible.

In fact, Williams and his assistant Tom Kilburn did it much quicker than anyone expected. In June 1948 a 'baby machine' was working. It could store 1024 bits on a cathode-ray-tube, enough to demonstrate the stored-program principle in working electronics, the first in the world to do so.

Man in the middle

Meanwhile in March 1948, Newman had offered Alan Turing a post. In May 1948 Turing gave up hope of the National Physical Laboratory turning his Universal Machine into practical reality (see this Scrapbook page for the ACE machine that Turing designed). He resigned from the NPL and accepted relocation to Manchester, where this breakthrough had rather unexpectedly been achieved.

The salary for Turing's post came from the Royal Society grant. He was formally 'Deputy Director' of the Royal Society Computing Machine Laboratory. The grounds for appointing him to this post, as minuted on 15 October 1948, were that

It was in his paper on 'Computable Numbers' (1936) that the idea of a truly universal machine was first clearly set out. This paper was written for purely theoretical and logical purposes, but Mr Turing has had over two years of practical experience since the war, as designer of the ACE machine which is now being constructed at the National Physical Laboratory.
Thus as the time of his appointment, the character of the Manchester machine as a practical version of the Universal Turing Machine was made clear. It was soon totally forgotten.

Who had the Idea?

The Manchester computer of 1948 was reconstructed for its fiftieth anniversary on 21 June 1998. It is now at the Manchester Museum of Science and Industry, with a description here.

The website created for this 1998 event continues to offer much information about how Williams and Kilburn succeeded with their cathode-ray-tube storage and built the machine.

Brian Napper, who wrote the material for the Manchester site, stressed in his page on the general background that the Manchester machine was built with programs loaded in RAM --- the revolutionary idea that defined the computer. (See this Scrapbook page.) But he did not explain how Williams and Kilburn got this idea.

It would have been possible for Williams to learn about the stored-program principle in the course of his 1946 work at TRE on the storage mechanism. It was generally in the air after the EDVAC report of 1945; and from Turing's ACE proposal. But what in fact happened, according to Williams (in the Radio and Electronic Engineer, July 1975) was that he learnt the principle from Newman after taking up the Manchester post in December 1946.

With this store available, the next step was to build a computer around it. Tom Kilburn and I knew nothing about computers, but a lot about circuits. Professor Newman and Mr A. M. Turing knew a lot about computers and substantially nothing about electronics. They took us by the hand and explained how numbers could live in houses with addresses and how if they did they could be kept track of during a calculation...

There is an obvious chicken-and-egg interdependence between logical function and practical engineering. Turing and Newman could not embody their ideas without engineers; the engineers would not have known what to build without the mathematicians' ideas.

The latter aspect is not always given its full weight.

Carry on Computing

At Bletchley Park, in building Bombes and the Colossus, the synthesis had been reasonably harmonious but it was not to be so at Manchester. There was a particularly Mancunian culture clash.

Alan Turing could not 'direct' anything, but he organised the software which made the engineers' machine work. In 1950 he completed a Programming Manual.

See this page of the Manchester history site for a guide to its editions.

A transcription into HTML of the complete manual.

A PDF file of the whole manual

These come with an introduction by the editor, Robert S. Thau, which adds comment on Turing's programming ideas and their context.

Turing's assistants on the software writing were women, Cicely Popplewell and Audrey Bates. This set-up neatly confirmed Manchester stereotypes:

hard soft
engineering mathematics
Williams, Kilburn Newman, Turing
things concepts
north south
Real ManchesterVirtual Womanchester

Has much changed? At least women in computing have put themselves on the agenda.

War Again

The British government agenda in 1949 was dominated by the atomic bomb. They didn't believe that the United States would retaliate against a Soviet nuclear attack on Britain, and they wanted to prove that Britain was still one of the Big Three. In 1946 the passage of the McMahon Act in the United States meant that Britain, which had given much to the wartime atomic bomb programme, was denied American co-operation thereafter. In late 1948, the Cold War began in earnest, and it became a British national priority to have computing facilities for the atomic bomb implosion calculation.

A lavish new contract was rushed through to allow Ferranti to build a full-scale machine, the Ferranti Mark 1. The contract specified merely that it would be built to Williams's design.

Newman's priorities for pure mathematics and science were forgotten.

Parallel machines

A version of Turing's ACE design was built at the National Physical Laboratory after all. The Pilot ACE was inaugurated in November 1950.

At this period the main rival to the Manchester computer development was the EDSAC computer at Cambridge, England, inaugurated in September 1949. This was the work of Maurice Wilkes, who took as his starting-point the American EDVAC proposals, but was able to beat the Americans at their own game.

Turing gave a talk at its inauguration which anticipated later ideas of program proof, but, in typical disregard for his own reputation, made nothing of it.

Martin Campbell-Kelly gives a description and simulator of the EDSAC.

Using the world's first computer

F. C. Williams himself had no interest in the use of the machine he had built. Speaking in an oral history of Pioneers of Computing, Science Museum, 1976, he said:
Well let's be clear right from the start, I never have been interested in computing, and I'm still not interested in computing. What I'm interested in is computers. I'm an engineer, I define the computer right from square one as a device which was designed to facilitate the performance of mathematics, the greater part of which would be very much better not done, and I've never changed that view really...

Users were seen as rather a nuisance while the machine was in development, but Newman immediately found a genuine mathematical problem that could be run on the prototype Manchester computer, and thereby rescued a little of the originally intended function for the machine in pure mathematics.

This was the problem of finding Mersenne primes.

At that time the largest known prime was 2127 − 1, and had been so since 1876, when Lucas discovered a test for primality of numbers of this type, a test which was extremely well suited to a computer. They ran a program successfully, and then Turing coded a faster version of it, but even so did not discover the next prime, which was out of range at 2521 − 1, and was found only in 1952.

The largest known prime now is again a Mersenne prime, and found by exactly the same method, only on a somewhat larger and faster computer).

The 1949 programme gained newspaper publicity for the Manchester computer, although (or because) readers of the day would have assumed prime numbers to be the epitome of pure mathematical uselessness. Nowadays these investigations are seen rather differently because of the connection between large primes and cryptographic security. As usual the mathematicians were ahead of their time.

It wasn't that either Newman or Turing had a particular research interest in Mersenne primes; the problem was chosen as one which could show off the power of the computer. But in 1950 Turing used the prototype computer for a problem which derived from his pre-war research work on the Riemann Zeta-function, also associated with the properties of prime numbers. This was probably the first serious use of a computer for research in mathematics. For Turing it also illustrated very neatly the power of the universal machine concept, as it performed the work for which he had designed a special-purpose calculator in 1939, now made completely redundant.

Intelligent Machinery comes out of the Closet

Although Newman made very careful statements to the press, Turing as usual announced rather incautiously that what they were interested in at Manchester was the extent to which a machine could think for itself.

Alan Turing was stimulated by the public controversy to write a definitive paper on his views for the prospects for Artificial Intelligence, or as he called it, Intelligent Machinery. This paper, introducing the idea of the Turing Test, was his only paper on the subject to be effectively published. He took the opportunity to air a kind of wit which could hardly have been more different from the heavy macho engineering ambience at Manchester, and in which male and female role-playing enjoyed a curious part.

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