Alan Turing: The Enigma (121 page)

Babbage’s work in 1837 first established the logical principle of digital computers. His ideas were developed further in Turing’s classical paper in 1936. The COLOSSUS machine produced by the Department of Communications of the British Foreign Office, and put into operation in December 1943, was probably the first system to implement these principles successfully in terms of contemporary electronic technology. … The requirement for the machine was formulated by Professor M.H.A. Newman, and the development was undertaken by a small team led by T.H. Flowers. A. Turing was working in the same department at that time, and his earlier work had its full influence on the design concept.

I assume that ‘the logical principle …’ means ‘conditional branching’. Although this makes sense as retrospective comment, it is not my impression that this analysis was formulated at the time, and still less that there is some document in GCHQ dating from 1943 with references to Babbage or to
Computable Numbers.
The first two sentences have rather the function of giving a suitably imposing rationale for ‘declassification’. The reference to AMT in the last sentence also seems to me to be misleading, except in the extremely general sense that he had done so much for the mechanisation of processes before Newman arrived. The essential part that AMT played in this development was in providing a statistical theory: not the machine, but the purposes for which it would be used.

(
5.8
) The third of only three wartime letters in
KCC.
The first, written in August 1941 while at Portmadoc, gave a few details of the holiday and a reference to the Dorothy Sayers book; the second, later in 1941, mentioned a week in Cambridge and meeting David Champernowne (‘Didn’t find any others I know except the old fogies’), slight bombing at Shenley, and a possible visit to Rossall to see to Bob’s future. I am grateful to Canon H.C.A. Gaunt for finding the dates of the Lake District holiday in A.C. Pigou’s diaries. These, incidentally, show that this was the only visit AMT made there except that in 1948.

(
5.9
) CAB 80/41. I found no further references to AMT in these or the corresponding American files.

(
5.10
) FO/850/256.

(
5.11
) Shannon had included it in the paper
submitted in 1940 (see note BP 8). Professor I.J. Good has written to the author: ‘The “sampling theorem” … is not due to Shannon although it is often attributed to him. It dates back at least to E.T. Whittaker,
Proc. Roy. Soc. Edin. 35
(1915).’

(
5.12
) As note 4.21.

(
5.13
) J. Ramsbottom,
Edible Fungi,
1943.

(
5.14
) These pages are in
KCC.
They begin in mid-sentence, and are bereft of the necessary definitions, so do not make much sense. But the underlying problem addressed by AMT was clearly that of finding ‘exceptional’ rotor wirings permutations with some symmetrical feature, leaving a non-randomness that the cryptanalyst could exploit. Such wirings would have to be avoided when constructing an Enigma-type machine. The pages also give a strong impression of the high-powered algebraic and statistical work he had done on rotor machines.

(
5.15
) Quoting from
The War Speeches of the Rt. Hon. Winston S. Churchill
(Cassell, 1951-2).

(
5.16
) According to
EST
he was actually ‘offered a lectureship’ at Cambridge in 1945, and M.H.A. Newman’s
Biographical Memoir
also states this. But the records of the Faculty Board lend no support to this claim. Most likely he was speaking to his mother of continuing as a Part III lecturer, just as he would have been in 1940 but for the war.

(
5.17
) In
Mind
, 1950 (see page 415 and note 7.34).

(
5.18
) In the ACE report (note 6.1).

(
5.19
) In
Intelligent Machinery
(note 6.53). These three quotations express ideas so fundamental, and so characteristic of his thought, that I believe the anachronism of setting them in summer 1945 is justified.

(
5.20
) Quoting from Mrs Turing’s words in
EST.
This is explicitly given as a nugget of recollection, even if given a maternal gloss of ‘service’. ( I have inserted ‘machine’ for her word ‘computer’, since in this context there is no distinction whatever in meaning, and I do not wish to introduce the word prematurely.)

(
5.21
) Reprinted fully in
Faster than Thought
(note 8.25).

(
5.22
) Quoting from letters in the von Neumann archive, Library of Congress, Washington DC.

(5.23) The relevant passage is in the extract included in
The Origins of Digital Computers
, ed. B. Randell (Springer Verlag, Berlin, 1973).

(
5.24
) This letter was to Col. L.B. Simon at the Ballistics Research Laboratory.

(
5.25
) Frankel’s letter was written to B. Randell in 1972, in connection with the latter’s detective work ‘On Alan Turing and the Origins of Digital Computers’. This paper, quoting Frankel’s letter, appeared in
Machine Intelligence 7
(Edinburgh University Press, 1972). See also note 5.26.

(
5.26
) Randell’s 1972 work (note 5.25), arose from the fact that the EDVAC report was supposed by everyone to be the
fons et origo
of the digital computer. In trying to see how the ACE ‘fitted in’, he came across an assertion by Lord Halsbury, writing in 1959 as managing director of the NRDC, that one of the most important events in the evolution of the modern computer was ‘of course the meeting of the late Doctors Turing and von Neumann during the war.’
(Computer Journal,
7, 1959).

Randell continued to stress this question of a meeting, but my own conclusion is that whether or not they happened to meet (and I have found no more evidence of a meeting than Randell did), Halsbury was mistaken in thinking it important. The story of AMT and von Neumann is that of two utterly different personalities, in different social environments, but drawn to parallel problems within the movement of mid-century science. Either figure was perfectly capable of assembling the necessary ideas for the digital computer out of the conjunction of Hilbertian rationalism and Second World War technology. Both did, responding in slightly different ways according to their circumstances. There is no gap on either side that needs to be explained by a meeting, or some other conspiracy theory of history. Much the same applies to the question of when and how AMT discovered Babbage’s work: it would have fascinated and encouraged him, but was ultimately irrelevant.

Mrs Turing got the picture exactly right when she wrote that his aim was ‘to see his logical theory of a universal machine, previously set out in
Computable Numbers
, take concrete form in an actual machine.’ Since she knew nothing of
Computable Numbers
but that a German professor had commended it, this was certainly not her own analysis; Newman could have guided her (see note 2.38) but her statement was more definite than anything that Newman had written. Most likely it was simply what AMT himself had told her again and again, trying to explain that all the logic she had thought so useless in the 1930s had come to something practical after all. The connection between 1936 and 1945 was also perfectly clear during AMT’s time at the NPL. It was only later that this simple and direct truth was forgotten, to the extent that in 1972 Randell, writing his historical paper, could see ‘no obvious connection’ between the Universal Turing Machine and the ACE; and mentioned the ACE report only in terms of its relationship to the EDVAC report. It is astonishing how difficult people have found it, both in AMT’s own time and since, to accept that he could both think of something abstract, and set out, without making any particular fuss, to make it concrete. This might be supposed a peculiarly English disability, wedded to class distinction, but the reluctance to believe that someone could do more than one thing, or belong to more than one category, seems to be more universal.

(
5.27
) Sir George Thomson, describing Sir Charles Darwin in a
Biographical Memoir of the Royal Society
, 1963.

(
5.28
) Here and frequently in the following narrative I draw on the collected minutes and reports of the Executive Committee of the NPL.

(
5.29
)
Nature
, 7 April 1945.

(
5.30
) Memorandum by J.R. Womersley, ‘ACE Project – Origin and Early History’, dated 26 November 1946, in DSIR 10/385. According to
EST:
‘On submission to the Government of the outline of his design for such a [universal] machine he was taken on to the staff … in October, 1945.’ While AMT might have given some kind of verbal description to Womersley, no formal ‘submission’ appears in the records and most likely Mrs Turing was going on the memory of AMT’s ACE report being formally accepted a few months later.

(
5.31
) Lyn Newman, in her introduction to
EST.

(
5.32
) Edward Carpenter s autobiography,
My Days and Dreams
(George Allen & Unwin, 1916).

(
5.33
) Forster’s article in
Tribune
was reprinted in
Two Cheers for Democracy
(as BP. 13), where it followed a 1942 essay on Tolstoy voicing similar thoughts: ‘Do you yourself believe in simplicity as a cure for our present troubles? And, if so, how do you think simplicity can be worked in a world that has become industrialised? Tolstoy’s outlook was agricultural: he never realised the implications of the machine’.

(
5.34
) Quoting from Angus Calder,
The People’s War
(Jonathan Cape, 1969).

Mercury Delayed

(
6.1
) AMT’s report was headed only ‘Proposed
Electronic Calculator’, and did not use the name ‘ACE’. But he used the name as soon as the report was discussed, and so to simplify matters I have called it ‘the ACE report’. A copy of the report, though without the pages of diagrams, is in DSIR 10/385, the main file covering the ACE development from 1946 to 1948. A complete version was issued in a limited edition by the Division of Computer Science, National Physical Laboratory, in April 1972 as report Com. Sci. 57. A first analysis of it was made in 1975 by B.E. Carpenter and R.W. Doran, later appearing in
Computer Journal 20
(1977).

(
6.2
) The fragments consist of just four typescript pages. They survive only because he used the reverse sides as scrap paper on which to explain some circuit theory to Mike Woodger in 1947.

(
6.3
) This was his lecture to the London Mathematical Society, 20 February 1947 (see page 356). The typescript (until now unpublished and unquoted) is in
KCC.
I have employed it here at the cost of jumping out of sequence, as I could hardly improve upon his own exposition of the ideas announced more starkly in the original ACE report.

(
6.4
) In January 1947 J.V. Mauchly pointed out the idea that ‘one set of instructions’ could ‘modify another set’. Paper reprinted in
The Origins of Digital Computers
(as note 5.23), page 366.

(
6.5
) Mike Woodger has told me of a reference in NPL files, since destroyed, to the ACE report being in existence by the end of 1945. But in any case it was ready in time for Womersley to compose his own report by 13 February 1946; this was essentially 1945 work.

(
6.6
) In the papers of Mike Woodger.

(
6.7
) Paper E.881 in the NPL Executive Committee records.

(
6.8
) Both letters are in DSIR 10/385.

(
6.9
) J.H. Wilkinson has described his association with AMT and the ACE project in an article in
The Radio and Electronic Engineer
, July 1975, in the
Pioneers of Computing
oral history, ed. C. Evans, Science Museum, London, 1975, and in a paper ‘Turing’s work at the National Physical Laboratory …’ in the Metropolis volume (see note 4.21).

(
6.10
) DSIR 10/385.

(
6.11
) Letter in the von Neumann archive, Library of Congress.

(
6.12
) Minutes of the Council of the Royal Society, 1946.

(
6.13
) S.S. Snyder,
Influence of US Cryptologie Organisation on the Digital Computer Industry.
Declassified NSA report SRH 003, 1977, available at the National Archives, Washington DC.

(
6.14
) H.H. Goldstine,
The Computer from Pascal to von Neumann
(Princeton University Press, 1972), mentions this visit and the ‘third version’ in passing on page 218. My study of the Goldstine archive at Hampshire College, Amherst, Mass., failed to locate the ‘third version’.

(
6.15
) Letter in the von Neumann archive, Library of Congress. My search revealed only one reference to AMT in von Neumann’s letters beside this glancing comment on the thesis of finitely many mental states’. It was in a letter to Wiener of 26 November 1946: ‘I did think a good deal about self-reproductive mechanisms. I can formulate the problem rigourously [sic], in about the style in which Turing did it for his mechanism. I can show that they exist in this system of concepts …’