viewpoints

Vdoi:10.1145/1562164.1562180 David P. Anderson Interview An Interview with Maurice Wilkes Maurice Wilkes, the designer and builder of the EDSAC—the first computer with an internally stored program—reflects on his career.

resented here are excerpts What was your role? from an interview with Sir The university took me on as the boy Maurice Vincent Wilkes, the who did the work! Analog computers developer of the Electronic were much in the air then and a differ- Display Storage Automatic ential analyzer was ordered. We were PCalculator (EDSAC), microprogram- starting up this mathematical labora- ming, symbolic labels, macros, and tory when I received an invitation to subroutine libraries. Wilkes, the 1967 join in the war effort working on radar. ACM A.M Turing Award recipient and Of course, I didn’t know the exact na- winner of the ACM lifetime member- ture of the work at the time of the invi- ship award, is a former member of tation but I was one of a small group of Olivetti’s Research Strategy Board people from the Cavendish who were and an emeritus professor at the Uni- let into the secret. versity of Cambridge Computer Labo- ratory in the U.K. David P. Anderson, Who was it that told you? Principal Lecturer in the History of It was [Robert] Watson-Wattb himself at Computing at the School of Creative the Air Ministry. So, I went off to do that, Technologies, University of Ports- deserting Lennard-Jones very ungrate- mouth, U.K., conducted the interview fully because he’d got it all fixed up. with Wilkes, 96, earlier this year. How did Lennard-Jones When did you first get react to losing you? involved with computers? Who was leading that activity? He didn’t mind—I went off anyway. Well, you’ve got to realize that although We had here [John] Lennard-Jonesa When I came back after the war, in Sep- there were no digital computers in the who was a great pioneer of structural tember 1945, I found myself tempo- immediate pre-war period, there was chemistry. And he and his small group rarily, but later permanently, head of a lot of digital computing. The impor- of very able people showed that in the Mathematical Laboratory. tance and power of it was beginning to spite of the computational bottleneck be recognized. you could, in fact, achieve quite signifi- How much latitude did you The actual computing was then on cant results. Lennard-Jones was a man have in deciding the priorities desk machines with people to work of much vision and he was successful of the laboratory? them, mostly research students, but pro- persuading the university to establish As head of the laboratory I didn’t have fessional computers were beginning to a computing laboratory, which was to ask people if I could do things. The be employed for organizations such as initially called a mathematical labo- overall terms of reference were to de- the army, for calculating range tables ratory. It was Lennard-Jones who gave velop mathematical methods and

Y B ill T h o mp son or firing tables as they were called in me my first opportunity to get practi- equipment for doing computation. So America. That was all beginning to cal experience of computing. that was all fine. As I had been doing

O GRAPH B grow up. Cambridge was a very lively T

PH O example of this digital computing. a Sir John Edward Lennard-Jones (1894–1954) b Sir Robert Alexander Watson-Watt (1892–1973)

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radar I didn’t know anything about the stored-program computer? day we did the first program and we’d what was going on with mathematical No, John Von Neumann wrote a report all got little programs ready to run. machines but I soon began to learn. on behalf of the group and [Leslie] Comrieg was given a copy in America How was computer development Did you have any help with your and he showed it to me. He lent it to viewed at Cambridge? education in computing machinery? me and I sat up all night reading it, so Oh I don’t know, I always like to make a I learned a great deal from [Douglas] it wasn’t the first time. joke and say that they thought we were Hartreec who was in touch with Ameri- mad and if, at a cocktail party, you en- can people and one day I had a tele- How did Comrie come to larged on your enthusiasm you would gram out of the blue from the Moore have a copy of the report? find people moving away from you! School at Philadelphia asking me to go They gave copies away to people who You see, I never tried to do any pros- to a course. I got there with great diffi- visited. Comrie’s copy is now in the li- elytizing, I simply built a computer. culty as crossing the Atlantic in those brary of the Computer Laboratory. days was no simple matter. I missed Did you have a clear sense the early part of the course. What did you do next? from the start of who your The first thing to do was to make sure users were likely to be? Did that cause you any an ultrasonic memory would work and They were all around me, they were serious difficulties? we did that by January 1947 and then we students who didn’t like spending No, I had got a singular set of qualifica- went ahead. weeks, or a week, or more computing. tions because I had done some comput- They rushed at a computer, even an ing as a student. I was one of the people This was quite a departure from unsatisfactory experimental one, as that worked a hand-operated calculating the pre-war work of the laboratory. EDSAC was to begin with. And it was machine. I was a thoroughly qualified Did you need any special through those students that the idea electronics person having done ham ra- permission to start this work? spread. They went to their supervisors dio and all that sort of thing. I had the Cambridge is a very strange place, and said “Look what I’ve done.” The mathematical background insofar as it there are little departments like mine, supervisors were duly impressed and was necessary for computing. and big ones like the Cavendish. But before very long important people in [John Presper] Eckertd and [John] from the administrative point of view Cambridge were saying that comput- Mauchlye were the instructors and they are on a level. That meant I didn’t ers were important. It was very low- they put me absolutely and fully in the have to ask anybody or make any pro- key, bottom-up, students-upward. picture. I heard them talking about posals. I was able to just go ahead and That’s not a bad way for ideas to stored-program computers—people do it. There were some funds that went spread. say the Von Neumannf computer, it’s with the lab in effect and I guessed that really the Eckert-Von Neumann com- more funds would become available in Did you have any concerns puter and I thought I might have a shot due course. about how the computer-building at building one. work of the laboratory would Did you have a large staff be funded going forward? Was that the first time that you at your disposal? Well, I assumed it would all happen. We had encountered the notion of No, no; very small. Most projects—in were a very low-cost outfit because we industry and university—depend on a didn’t have a lot of the mathematicians c Douglas Rayner Hartree (1897–1958) small handful of three or four people and people on the payroll for the sake d John Presper Eckert Jr. (1919–1995) and we had less than that to provide of the money and I was in 100% charge, e John William Mauchly (1907–1980) the drive. There were a lot of people which made it very easy. f John von Neumann (1903–1957) who were paid on the funds, math- ematicians and other hangers-on and Am I correct in thinking that there were also a number of assistants. the initial capital budget or the Although there were We had instrument makers and elec- laboratory in 1936 was around tronic people on the assistant level. £10,000? no digital computers But I was the one who brought all the Yes. in the immediate information about computers into it so there was no argument with me you That was a very large pre-war period, see; it all came from me. I had a very sum at the time. there was a lot of loyal team and so we went ahead. It was. Lennard-Jones was a man of enormous vision and although analog digital computing. How long was it before you computers were in the air the labora- achieved some success? tory was not biased toward analog com- The EDSAC began to work in the sum- puters. We could drop them as soon as mer of 1949 on May 6th. That was the it appeared that they didn’t work out and I could go ahead and build a stored- g Leslie John Comrie (1893–1950) program computer.

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That must have been a very er and we both got the highest honors liberating environment you could. So that was all right. in which to work? He was a real mathematician except Very. Yes, it was a very responsible one. that he only learned one little bit of I mean no one else in the laboratory mathematics and then didn’t learn any was sure that it was going to work but I more. He was no practical organizer was the one who could see it first. And and, well, if you had Turing around in so you see, we then had an enormous the place you wouldn’t get it going. advantage. This is what really gave us the edge. Because quite a number of That certainly wasn’t a these computers, especially the one in problem with the EDSAC. Manchester, were beginning to work at No, I mean we just barged ahead on the same time. But they all had to hire the EDSAC and the rule was that if an engineer to build a computer for you had got something that would them but that wasn’t the case with me. work you didn’t spend another hour I was fully qualified on both sides. on making it simpler or cheaper, you I got a group of students working on went ahead with it. programming before the computer It demanded very strict discipline was running and so we could make a M.V. Wilkes during EDSAC I construction; and keeping your eye on the ball. There very quick and rapid transition to the EDSAC I became operational in 1949. were all sorts of interesting things to user side and that was where we got the complex logic we didn’t have complex follow up but we resisted them. edge. logic. We all had very simple logic in We concentrated on the one ob- the early days. Eckert is on record some- jective with no demonstrations on Could you say a little about where saying that he looked at Boolean the way. We didn’t need to show that the different contributions algebra but it didn’t seem to him to be the ultrasonic memory would work. mathematicians and engineers useful. None of the practical people I mean when the electronics end, made to early attempts to made much use of Boolean algebra but it was working that was sufficient. build computers? Was there it was regarded as absolutely essential Whereas, you see, at Manchester any tension between them? to the mathematicians. But there was a they had an electrostatic storage Well, of course. Mathematicians tension between them that is perfectly depending on quantum theory and weren’t particularly well qualified. true. they had to be very sure that it would They’d all done a bit of numerical work. It was [Tom] Kilburn’sj idea analysis but it wasn’t the same as digi- Did that give rise to any problems to build a ‘Baby’. He was able to do tal computing. I think perhaps tension at Cambridge or elsewhere? it. Validating the memory was what arose from entirely different back- Of course so many of the physicists the Baby was all about. It was abso- grounds. Take the question of Boolean of the period had been through the lutely essential because they had to algebra. Mathematicians often write mathematical tripos that was one of validate it not for themselves but for and speak as though Boolean algebra its strengths. But not all of them, many their sponsors. and mathematical logic was at the ba- Cavendish people and supervisors like I wasn’t troubled with sponsors. sis of computing but it wasn’t that [John Ashworth] Ratcliffeh had no un- Somehow the money came. way at all. The mathematicians did not derstanding of mathematics. y permi ss i o N understand switching really, electronic I was ensconced in the four walls To what extent would you say switching; the engineers did. of a computer laboratory and I never that the work of [Charles] Mathematicians, when it was point- counted myself as a mathematician. Babbagek was significant in ed out to them, that Boolean algebra Von Neumann, of course, rather de- shaping the early development modeled electronic switching at once spised engineers. He got on with them of stored-program computers? understood and because they could un- all right but I don’t think he regarded I didn’t know anything about Babbage. y o f C ambridge . R epr duced b derstand digital switching to a certain them as important for such matters as People started writing letters to the degree by understanding mathematical having credit for what they were doing. Times and Hartree got interested and I logic, they assumed that everyone would [Alan] Turingi was an exact contem- remember him coming into our build- y, Un iver s it y,

o r look at it that way. porary of mine and that means that I ing with a copy of Babbage’s memoirs Whereas engineers, when they don’t have to regard him as a great man in his hand. It was Hartree who got ab o rat were first told about Boolean algebra, because you don’t regard your contem- me interested in Babbage. Of course, thought “What a daft idea this all is!” poraries as great men. I don’t remem- Babbage never had the concept of the and it was only later when Shannon told ber him very clearly from the under- stored program, instructions being them about the connection that they graduate days but he was certainly in coded as numbers; Babbage certainly Y RIGHT Co mputer L saw any use for Boolean algebra. the class and we took the tripos togeth- wasn’t influencing me. But there wasn’t any use. Boolean

O GRAPH C P gebra has no time element to it and T al h John Ashworth Ratcliffe (1902–1987) j Tom Kilburn (1921–2001)

PH O while it is good for shaking up a bit of i Alan Mathison Turing (1912–1954) k Charles Babbage, FRS (1791–1871)

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Looking back, what would Did Newman’s involvement even in the most general terms? you say was the significance with the Colossus have any No, and I don’t think Williams would of Turing’s 1936 Entscheidungs- effect on developments at have been interested in the technol- problem paper? Manchester do you think? ogy because, as I say, when technology I always felt people liked to make a No, I don’t think Williams would have moves, it moves very fast. And the tech- song and dance. Something like the been interested in the technology be- nology that was used in the Colossus doctrine of the Trinity involved where- cause, as I say, when technology moves, was very different from the sort of tech- as to an engineer you’ve only got to be it moves very fast. And the technology nology that took root in Bawdsey. told about the stored program idea and that was used in the Colossus was very you’d say at once “That’s absolutely different from the sort of technology that Another important figure at first-rate, that’s the way to do it.” That took root in Bawdsey [radar station]. Manchester at that time was was all there was to know. Patrick Blackett.o Did you have There was no distinction in that pa- Was there any rivalry between the anything to do with Blackett? per that had any practical significance. various computer-building projects Blackett? Oh, I knew Blackett, he was He was lucky to get it published at all about who would get there first? always very nice to me. He said he but I’m very glad he did. I mean [Alon- Well, as I always say, it was a funny race didn’t know anything about computers zo] Churchl had got the same result by because we were all aiming at different and that was perfectly true. He was of other methods. finishing points. You see, we wanted an age. Above a certain age people are I liked Turing; I mean we got on very something that was business-like and never really happy with computers. well together. He liked to lay down the would fit into this existing digital envi- law and that didn’t endear him to me ronment. Eckert and Mauchly wanted He helped Williams and but he and I got on quite well. People to produce a commercially viable com- Newman though? sometimes say I didn’t get on with Tur- puter and I don’t quite know what Wil- Well, he was a busybody so he would ing but it’s just not true. But then I was liams wanted to do. He had no perma- be everywhere. He was very energetic very careful not to get involved. nent interest in computers. He wasn’t and he knew how to get things done. very interested in computers at all. He He thought socialism was a great thing, Was he a difficult man with was interested in showing that CRT whereas I thought socialism was a whom to get along? memory would work but I don’t think great mistake and indeed it was. Yes, I think that’s probably true and he he had any interest beyond that and he was not in any sense a team leader. He handed it over to Kilburn who made What have you found most didn’t know how to get things done. very good use of it. Kilburn was a very, surprising about the developments Of course I had another advantage very great success. that have taken place in there. I had war service, six years of computers since 1949? it, and I had done real staff jobs and What are your recollections Well, of course, it’s the speed. We had that teaches you a lot about how to get of Kilburn? great vision, we saw that computers things done. [Max] Newmanm was a I knew him very well. Of course we were going to be a big thing, not only great admirer of Turing. But he was not were very good friends and we were for arithmetic calculation but in oth- in the line management of the comput- both determined that we wouldn’t al- er things as well, business and what- ing work; I mean Newman was never low any Manchester-Cambridge rival- not. We had great vision but we could an engineer. The professor of electrical ries to show up in our groups and we have no idea of timescale. For one engineering did that. achieved that on the whole, I mean we thing, young men don’t but the oth- always had a high respect for each oth- er reason was of course we couldn’t [Freddie] Williams?n er. It could so easily have happened, see the coming of semiconductors. Yes, everybody at TRE [Telecommuni- you know. But it didn’t and that was Now semiconductors have given cations Research Establishment] had due to Kilburn’s common sense really us various things, small size, small some experience of management. Wil- and mine. It was very important but I cost, high power but the important liams was in charge of the computer at mean we were complimentary. thing they have given us is reliability. Manchester and he was a very strong- We used to pray for reliability—our minded person. Mind you he was a What was Kilburn’s prayer was answered. In my lectures leader too—he ran it like a dictator! interest in computers? on this sort of thing I say that it was You can’t design or build a computer He was interested in providing a com- St. Theresa who was credited with unless you’re an engineer. I mean that’s puting service as I was. the remark that it is prayers that are what you mean by being an engineer. answered that create more problems Newman exerted very little influence on Returning to Newman for a than those that aren’t! what went on in Manchester. Williams moment. We now know that saw to that all right. in 1945, Newman took Willis- Jackson, who was William’s o Lord Patrick Maynard Stuart Blackett (1897– predecessor, to Bletchley Park to 1974) l Alonzo Church (1903–1995) m Maxwell Herman Alexander Newman (1897–1984) see the Colossus. Did Newman ever n Sir Frederic Calland Williams (1911–1977) discuss the Colossus with you— Copyright held by author.

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