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Professor I J Good

Jack Good was the first Atlas/Trinity Fellow. Before the 1939-45 war, he had completed a doctorate at Cambridge under the direction of G H Hardy. During the war (1941 onwards) he worked at the Government Code and Cypher School at Bletchley Park with Hugh Alexander, Max Newman, Alan Turing and many others. He arrived on the 27th May, 1941 which was the day that the Bismark was sunk. Although the Luftwaffe and Army Enigma codes had been broken, the Naval Enigma was still to be broken. He worked in Hut 8 where the Bombes built by the British Tabulating Company (later to become ICT and take over Ferranti) were being used for code breaking. At the time, a new set of machines called the Robinsons (after (Heath Robinson) were being introduced. Jack Good worked at Bletchley throughout the war.

After the war, Jack joined Max Newman at Manchester University in the period when the Ferranti Mark I was being designed. Tom Kilburn arrived later and was the main engineer for the Baby machine.

In 1948, he moved to the Government Communications Headquarters (GCHQ) and in 1959 to the Admiralty Research Laboratory. A mischevious character, he even managed to publish an article by I. J. Good and K. Caj Doog, his name spelt backwards!

He joined the Atlas Computer Laboratory in 1964 as the first Atlas/Trinity College, Oxford Fellow. Some of his publications during this period were:

• The human preserve (1964)
• Categorization of classification (1965)
• The generalization of Lagrange's expansion and the enumeration of trees (1965)
• Logic of man and machine (1965)
• The probability of war (1966)
• Human and machine logic (1967)
• A New Conjecture Related to the Riemann Hypothesis (1968)

In 1967, he became University Distinguished Professor at Virginia Polytechnic Institute and State University (Virginia Tech). He was a prolific author with over 900 papers to his credit. He gained the IEEE Computer Society's Computer Pioneer Award in 1998 for his work in code breaking technology during World War II. His work led to the development of the first working special purpose, electronic computers and the first computer to be controlled by an internally stored program.

Jack Good at Virginia Polytechnic

A good synopsis of Jack Good has been written by John Lee.

Excerpts: Acceptance Speech for the 1998 Computer Pioneers Award from the IEEE

During the war, I was a cryptanalyst working at Bletchley park in England at a salary of about $1000 a year. Cryptanalysis is the analysis of the opponent's cryptographic system. Two of the main cryptographic machines used by the Germans were the Enigma and a machine, the SZ42, which we called Fish. (There was a third one called Sturgeon.) the Enigma had three (later four) wheels each wired from one face to the other, whereas Fish had twelve wheels with pins on their circumference, each denoting a binary digit, zero or one. the wheel patterns varied from one communication link to anotther and from one period of time to another period. In the Naval Enigma, the three (or four) wired wheels were selected from a set of library of eight wheels, so there were 8 × 7 × 6 = 336 possible wheel orders on a given day.

I joined Bletchley park in May 1941 and was put in the Naval Enigma section called Hut 8. The reading of the Naval enigma was probably essential for winning the Battle of the Atlantic, the battle against U-boats, the German submarines. The heads of Hut 8 were the famous Alan Turing and later the British chess champion Hugh Alexander. Hugh was extremely intelligent but he never believed that a computer would ever play a good game of chess.

The keys for the Naval Enigma were cahnged every second day. One of the cryptanalytic methods was the method called cribbing, familar to all cryptanalysis, of guessing stretches of language. I was part of a team of about ten people who worked on another method. It was a statistical method invented mainly by Turing and called Banburismus because the stationery was printed in the town of Banbury. The method was, I believe, the first example of sequential analysis, at least the first notable example, and preceded Abraham Wald by two years.

. . .

When I arrived at Bletchley, Banburismus was already in use. I had an extremely simple idea that cut the work by about 50%. It was the replacement of scores such as 3.6 decibans (stored as 36 centibans) by 7 half-decibans. Nearly all the entries, of which there were a few thousand, could then be expressed by a single digit. I calculated that the expected loss of weight of evidence from this change would be small. Some months later I had another statistical idea for quickly identifying which of nine so-called bigram tables was in use on a given day. The day's work on Banburismus couldn't be started until the bigram table was identified. This method of identification was needed because an earlier method due to Turing had become obsolete.

. . .

Banburismus ceased to be of value by about April 1943 after two years of use. i was then transferred to the Newmanry, the section headed by M H A Newman, FRS, where machine methods were used for the daily work on Fish. After the war, Newman built a very strong Department of Mathematics at Manchester. The Newmanry was never called the Fishery perhaps because there was another section headed by Major Tester where hand methods were used against the Fish. Among the people in the Testery were Roy Jenkins, later a Chancellor of the Exchequer, and Peter Benenson, prominent in Amnesty International.

. . .

The first cryptanalytic assistant to Max Newman was Donald Michie. I was the second one and eventually the team had at least sixteen members. When I arrived in the Newmanry the fairly small crypanalytic machine being used, for setting the wheels for the messages, was called Heath Robinson. it made use of two teleprinter tapes, one containing an enciphered message and the other containing information about the key or wheel patterns. both tapes ran simultaneously on pulleys at high speed. often the tapes would break or mistakes were made in the preparation of the tapes, or the machine would break down. Sometimes one could diagnose the machine fault by the sounds it made or by the smell when it was trying to catch fire. Because of all these troubles, the future of the Newmanry was in the balance.

I produced significance tests for the runs and also insisted on much more careful checking. I adopted the saying If it's not checked, it's wrong. Donald has recalled that we collected relevant statistics of the texts of partially broken German messages, perhpas partly from work done in the testery. Consequently, Heath Robinson had a few successes, usually with big delays, but just enough to save the section, and to justify the building of a much better and much bigger machine, the Colossus. One of the advantages of Colussus was that the data on the key tapes were represented electronically inside the machine. this avoided most of the tape preparation and therefore saved a great deal of time. This was a suggestion of tom Flowers, who became the head engineer. he should have been knighted. he knew that thermionic valves or at least the gas-filled ones called thyratrons, are reliable if they are left on all the time A valve would either die early or it would have a long life. mark I had about 1500 valves. it was the first large-scale electronic computer, but not general purpose.

. . .

Newman appointed me as the equivalent of an associate Professor of Mathematics at Manchester university, with part-time interest in electronic computing. he hired David Rees also, but David said he soon lost interest in the project. Later F C Williams, Tom Kilburn and other engineers were appointed. I cooperated well with Kilburn but only part-time. The first machine built was called the baby machine. It incorporated the Williams Tube, an adaption of a cathode-ray tube. it stored 256 binary digits at first and this was increased to 1024. Newman asked the engineers to stop trying to improve the Williams Tube and actually build a computer. It was completed on june 21, 1948. It was the first internally stored-program electronic computer and was a prototype for the large-scale Manchester Computer whose slang name was MADAM or MADM, the Manchester Automatic Digital Machine. i mad a proposal, at Kilburn's request, for the basic mathematical instructions for the Baby machine, roughly programmed in terms of the micro-operations of the machine.

Because of the Cold war, I resigned from manchester and rejoined the Civil service about twelve weeks before the Baby machine was completed.

. . .

I have kept my rather untidy notes that I made in my period in Manchester. In these notes, one of the ideas in February 1947 was what I called Machine-building in quotes. It anticipated Microprogramming which was independently proposed a few years later, and in more detail, by M V Wilkes. But my proposal was intended for the user of a computer not for the engineer. that was the reason for the quotes. The idea was to allow the user to desigb his own basic instructions for some large project in terms of the primitive micro-operations of the computer. This was a natural idea for anybody who had worked with Colussus. I have selected 17 further items from those Manchester notes written in 1947 and 1948, namely:

1. An emphasis on the value of having several accumulators not just one. Today this is standard even in hand-held computers such as the Hewlett-Packard 15C.
2. A suggestion for distinct subroutines for a given job, depending on whether it is more important to save time or to save space.
3. A proposal that, for the purpose of checking programs, a single binary digit could indicate whether a word represents a number or an instruction.
4. Examples of some programs that could be run on the Baby, and how.
5. A rough classification of the components of the machine and a proposed block diagram (June 1947).
6. A suggestion that the length of a word should be 40 binary digits instead of 32 so that two basic instructions could be packed into one word. this was adapted for the Baby and also for MADAM. In those days computers had very small memories so the packing was important.
7. How a puzzle called the Tower of hanoi could be run on the Baby
8. Calculations showing the need for all the mercury delay-line storage units to be of the same temperature within one degree Centigrade (being used on the computers at NPL and Cambridge).
9. I made the suggestion of returning to instruction number x+1 automatically after performing a routine following instruction x.
10. A request for flexibility in design with a facility for adding new basic instructions after the computer is complete.
11. Proposed a form of variable-length multiplication to compromise between accuracy and running time.
12. Proposed random rounding off for finding the effects of rounding without laborious mathematical analysis.
13. On August 8, 1948, after I left Manchester, in a letter to Newman I distinguished between centralized and decentralized computers. In a centralized machine, the result of each calculation passes through a particular register or accumulator. My block diagram for the Baby machine was for a centralized machine, wheras Kilburn's was decentralized. I said the brain is a centralized machine except when it uses only unconscious processes.
14. In the same letter, I drew Newman's attention to the advantages of magnetic drums over Williams tubes and mercury delay lines. Magnetic drums were adopted by Williams and Kilburn for MADAM, some time after June 21, probably independently of my letter to Newman.
15. In letters to turing, on September 16 and October 3, 1948, I mentioned the idea of resonance circuits in the brain; especially as a method for noticing analogies. . . . In the postscript I discussed chess-playing machines, which he and I had discussed in 1941, and gave a reasonable definition of a forced variation. I took for granted the need to distinguish between quiescent and non-quiescent positions. Shannon's paper on chess appeared in 1950.
16. In a letter to F C Williams in July 1951 I said A facetious question is whether it is intended to display chess positions on the monitoring tubes. Of course today it is no longer at all facetious.
17. On 1948 february 27, Williams and Kilburn asked me whether one was likely to return often in a short time (a) to a single word, (b) to a single stretch of words (of length of say 32 words), (c) to adjacent words. The engineers didn't like such things. I replied that for (b) and (c) the difficulty could be very largely removed by numbering the words so that consecutive words were in consecutive tubes instead of in consecutive rows of the same tube. Regarding (a), they didn't like say 32 occurrences in 128 words - this would seldom happen except for short iterative processes required several times. I suggested that this difficulty could be removed by having an additional elementary instruction, wait five periods, to be used whenever there is a danger of (a) occurring.