An Interview With Edsger W. Dijkstra

http://cacm.acm.org/magazines/2010/8/96632-an-interview-with-edsger-w-dijkstra/fulltext


==When did you first visit the U.S.?==

My first trip to the U.S. was in 1963. That was to an ACM Conference in Princeton. And I visited a number of Burroughs offices; that was the first time I met Donald Knuth. I must already have had some fame in 1963, because there was an ACM workshop with about 60 to 80 participants and I was invited to join. And they paid me $500. I didn't need to give a speech, I didn't need to sit in a panel discussion, they just would like me to be there. Quite an amazing experience.

==What about your first two trips to America surprised you about the profession?==

Well, the first lecture at that ACM workshop was given by a guy from IBM. It was very algebraic and complicated. On the blackboard he wrote wall-to-wall formulae and I didn't understand a single word of it. But there were many people that joined the discussion and posed questions. And I couldn't understand those questions either. During a reception, I voiced my worry that I was there on false premises. "The first speaker, I did not understand a word of it." "Oh," he said, "none of us did. That was all nonsense and gibberish, but IBM is sponsoring this, so we had to give the first slot to an IBM speaker." Well, that was totally new for me. Let's say that the fence between science and industry, the fence around a university campus, is here [in the U.S.] not as high as I was used to.


==What were other differences between Europe and the U.S.?==

One of the things that saved Europe was that until 1960 or so, it was not considered an interesting market. So we were ignored. We were spared the pressure. I had no idea of the power of large companies. Only recently I learned that in constant dollars the development of the IBM 360 has been more expensive than the Manhattan Project.

I was beginning to see American publications in the first issue of Communications of the ACM. I was shocked by the clumsy, immature way in which they talked about computing. There was a very heavy use of anthropomorphic terminology, the "electronic brain" or "machines that think." That is absolutely killing. The use of anthropomorphic terminology forces you linguistically to adopt an operational view. And it makes it practically impossible to argue about programs independently of their being executed.

==Is this why artificial intelligence research seemingly doesn't take hold in Europe?==

There was a very clear financial constraint: at the time we had to use the machines we could build with the available stuff. There is also a great cultural barrier. The European mind tends to maintain a greater distinction between man and machine. It's less inclined to describe machines in anthropomorphic terminology; it's also less inclined to describe the human mind in mechanical terminology. Freud never became the rage in Europe as he became in the United States.


==You've said, "The tools we use have a profound and devious influence on our thinking habits, and therefore on our thinking abilities."==

The devious influence was inspired by the experience with a bright student. In the oral examination we solved a problem. Together we constructed the program, decided what had to be done, but very close to the end, the kid got stuck. I was amazed because he had understood the problem perfectly. It turned out he had to write a subscripted value in a subscript position, the idea of a subscripted subscript, something that was not allowed in FORTRAN. And having been educated in FORTRAN, he couldn't think of it, although it was a construction that he had seen me using at my lectures.

==So the use of FORTRAN made him unable to solve that?==

Indeed. When young students have difficulty in understanding recursion, it is always due to the fact that they had learned programming in a programming language that did not permit it. If you are now trained in such an operational way of thinking, at a given moment your pattern of understanding becomes visualizing what happens during the execution of the algorithm. The only way in which you can see the algorithm is as a FORTRAN program.


==In 1963 Peter Patton, in Communications of the ACM, wrote that European programmers are fiercely independent loners whereas Americans are team players. Or is it the other way?==

At the Mathematical Centre, we used to cooperate on large projects and apply a division of labor; it was something of a shock when I went to the Department of Mathematics at Eindhoven where everybody worked all by himself. After we had completed the THE System, for instance, Nico Habermann wrote a thesis about the Banker's Algorithm, and about scheduling, sharing, and deadlock prevention. The department did not like that because it was not clear how much he had done by himself. They made so much protest that Cor Ligtmans, who should have written his Ph.D. thesis on another aspect of THE System, refused to do so.

==Is the outcome of the curricula different in Europe and America?==

I must be very careful with answering this because during my absence, the role of the university, the financing of the university, and the fraction of the population it is supposed to address have changed radically. That already started in the 1970s. So whatever I say about the [European] university is probably idealized by memory. Yes. But a major difference was that the fence around the university campus was higher. To give you an example, when we started to design a computing science curriculum in the 1960s, one of the firm rules was that no industrial product would be the subject of an academic course. It's lovely. This immediately rules out all Java courses, and at the time it ruled out all FORTRAN courses. We taught ALGOL 60, it was a much greater eye-opener than FORTRAN.


==Is there a relationship between the curriculum and the nature of funding of universities?==

Yes. It has the greatest influence on the funding of research projects. Quite regularly I see firm XYZ proposing to give student fellowships or something and then, somewhere in the small print, that preference will be given to students who are supervised by professors who already have professional contact with the company.

==Why do computer science departments often come out of electrical engineering in the U.S.—but not in Europe?==

A major reason is timing. For financial reasons, Europe, damaged by World War II, was later. So the American computing industry emerged earlier. The computing industry asked for graduates, which increased the pressure on the universities to supply them, even if the university did not quite know how. In many places, departments of computer science were founded before the shape of the intellectual discipline stood out clearly.

You also find it reflected in the names of scientific societies, such as the Association for Computing Machinery. It's the British Computer Society and it was the Dutch who had Het Nederlands Rekenmachine Genootschap; without knowing Dutch, you can hear the word "machine" in that name. And you got the departments of Computer Science. Rather than the department of computing science or the department of computation. Europe was later, it coined the term Informatics. Tony Hoare was a Professor of Computation.

comments powered by Disqus