Edsger W. Dijkstra: Programming

“How do we convince people that in programming simplicity and clarity —in short: what mathematicians call "elegance"”

Edsger W. Dijkstra

are not a dispensable luxury, but a crucial matter that decides between success and failure?
1980s
Source: EWD648.

People

“A programmer? But was that a respectable profession? For after all, what was programming? Where was the sound body of knowledge that could support it as an intellectually respectable discipline? I remember quite vividly how I envied my hardware colleagues, who, when asked about their professional competence, could at least point out that they knew everything about vacuum tubes, amplifiers and the rest, whereas I felt that, when faced with that question, I would stand empty-handed.”

Edsger W. Dijkstra

Dijkstra (1972) The Humble Programmer http://www.cs.utexas.edu/users/EWD/transcriptions/EWD03xx/EWD340.html (EWD340).
1970s
Context: After having programmed for some three years, I had a discussion with A. van Wijngaarden, who was then my boss at the Mathematical Center in Amsterdam, a discussion for which I shall remain grateful to him as long as I live. The point was that I was supposed to study theoretical physics at the University of Leiden simultaneously, and as I found the two activities harder and harder to combine, I had to make up my mind, either to stop programming and become a real, respectable theoretical physicist, or to carry my study of physics to a formal completion only, with a minimum of effort, and to become....., yes what? A programmer? But was that a respectable profession? For after all, what was programming? Where was the sound body of knowledge that could support it as an intellectually respectable discipline? I remember quite vividly how I envied my hardware colleagues, who, when asked about their professional competence, could at least point out that they knew everything about vacuum tubes, amplifiers and the rest, whereas I felt that, when faced with that question, I would stand empty-handed. Full of misgivings I knocked on van Wijngaarden’s office door, asking him whether I could “speak to him for a moment”; when I left his office a number of hours later, I was another person. For after having listened to my problems patiently, he agreed that up till that moment there was not much of a programming discipline, but then he went on to explain quietly that automatic computers were here to stay, that we were just at the beginning and could not I be one of the persons called to make programming a respectable discipline in the years to come? This was a turning point in my life and I completed my study of physics formally as quickly as I could. One moral of the above story is, of course, that we must be very careful when we give advice to younger people; sometimes they follow it!

Question , Support , Knowledge , Envy

“Program testing can be used to show the presence of bugs, but never to show their absence!”

Edsger W. Dijkstra

Dijkstra (1970) " Notes On Structured Programming http://www.cs.utexas.edu/users/EWD/ewd02xx/EWD249.PDF" (EWD249), Section 3 ("On The Reliability of Mechanisms"), corollary at the end.
1970s
Variant: Program testing can be a very effective way to show the presence of bugs, but it is hopelessly inadequate for showing their absence.

“The required techniques of effective reasoning are pretty formal, but as long as programming is done by people that don't master them, the software crisis will remain with us and will be considered an incurable disease. And you know what incurable diseases do: they invite the quacks and charlatans in, who in this case take the form of Software Engineering gurus.”

Edsger W. Dijkstra

Dijkstra (2000) "Answers to questions from students of Software Engineering" http://www.cs.utexas.edu/users/EWD/transcriptions/EWD13xx/EWD1305.html (EWD 1305).
2000s

People , Disease

“It is practically impossible to teach good programming to students that have had a prior exposure to BASIC: as potential programmers they are mentally mutilated beyond hope of regeneration.”

Edsger W. Dijkstra

1970s, How do we tell truths that might hurt? (1975)

Hope

“Please don't fall into the trap of believing that I am terribly dogmatic about [the go to statement]. I have the uncomfortable feeling that others are making a religion out of it, as if the conceptual problems of programming could be solved by a simple trick, by a simple form of coding discipline!”

Edsger W. Dijkstra

Dijkstra (1973) in personal communication to Donald Knuth, quoted in Knuth's "Structured Programming with go to Statements".
1970s

Religion , Feeling , Problem

“When we take the position that it is not only the programmer's responsibility to produce a correct program but also to demonstrate its correctness in a convincing manner, then the above remarks have a profound influence on the programmer's activity: the object he has to produce must be usefully structured.”

Edsger W. Dijkstra

Dijkstra (1970) " Notes On Structured Programming http://www.cs.utexas.edu/users/EWD/ewd02xx/EWD249.PDF" (EWD249), Section 3 ("On The Reliability of Mechanisms"), p. 6.
1970s

“We must not forget that it is not our [computing scientists'] business to make programs, it is our business to design classes of computations that will display a desired behaviour.”

Edsger W. Dijkstra

1970s, The Humble Programmer (1972)

Business , Forgetting

“How do we convince people that in programming simplicity and clarity —in short: what mathematicians call "elegance"— are not a dispensable luxury, but a crucial matter that decides between success and failure?”

Edsger W. Dijkstra

1980s
Source: EWD648.

People , Failure , Success

“There are very different programming styles. I tend to see them as Mozart versus Beethoven. When Mozart started to write, the composition was finished. He wrote the manuscript and it was 'aus einem Guss' (from one cast). In beautiful handwriting, too. Beethoven was a doubter and a struggler who started writing before he finished the composition and then glued corrections onto the page. In one place he did this nine times. When they peeled them, the last version proved identical to the first one.”

Edsger W. Dijkstra

Dijkstra (2001) Source: Denken als discipline https://www.youtube.com/watch?v=-Uae9_pgZzE#t=280, a program from Dutch public TV broadcaster VPRO from April 10th, 2001 about Dijkstra
2000s

Beauty , Time

“In the good old days physicists repeated each other's experiments, just to be sure. Today they stick to FORTRAN, so that they can share each other's programs, bugs included.”

Edsger W. Dijkstra

1970s, How do we tell truths that might hurt? (1975)

“As economics is known as "The Miserable Science", software engineering should be known as "The Doomed Discipline", doomed because it cannot even approach its goal since its goal is self-contradictory. (…) Software engineering has accepted as its charter "How to program if you cannot.”

Edsger W. Dijkstra

Dijkstra (1988) " On the cruelty of really teaching computing science http://www.cs.utexas.edu/users/EWD/transcriptions/EWD10xx/EWD1036.html (EWD1036).
1980s

Science

“As a result of a long sequence of coincidences I entered the programming profession officially on the first spring morning of 1952, and as far as I have been able to trace, I was the first Dutchman to do so in my country.”

Edsger W. Dijkstra

1970s, The Humble Programmer (1972)

Spring , Country

“Programming is one of the most difficult branches of applied mathematics; the poorer mathematicians had better remain pure mathematicians.”

Edsger W. Dijkstra

1970s, How do we tell truths that might hurt? (1975)

Mathematics

“Our intellectual powers are rather geared to master static relations and … our powers to visualize processes evolving in time are relatively poorly developed. For that reason we should do (as wise programmers aware of our limitations) our utmost to shorten the conceptual gap between the static program and the dynamic process, to make the correspondence between the program (spread out in text space) and the process (spread out in time) as trivial as possible.”

Edsger W. Dijkstra

Dijkstra (1968) " A Case against the GO TO Statement http://www.cs.utexas.edu/users/EWD/ewd02xx/EWD215.PDF" cited in: Bill Curtis (1981) Tutorial, human factors in software development. p. 109.
1960s

Time

“The competent programmer is fully aware of the strictly limited size of his own skull; therefore he approaches the programming task in full humility, and among other things he avoids clever tricks like the plague.”

Edsger W. Dijkstra

Dijkstra (1972) The Humble Programmer http://www.cs.utexas.edu/users/EWD/transcriptions/EWD03xx/EWD340.html (EWD340).
1970s

“Don't blame me for the fact that competent programming, as I view it as an intellectual possibility, will be too difficult for "the average programmer" — you must not fall into the trap of rejecting a surgical technique because it is beyond the capabilities of the barber in his shop around the corner.”

Edsger W. Dijkstra

Dijkstra (1975) Comments at a Symposium http://www.cs.utexas.edu/users/EWD/transcriptions/EWD05xx/EWD512.html (EWD 512).
1970s

“The art of programming is the art of organizing complexity, of mastering multitude and avoiding its bastard chaos as effectively as possible.”

Edsger W. Dijkstra

Dijkstra (1970) " Notes On Structured Programming http://www.cs.utexas.edu/users/EWD/ewd02xx/EWD249.PDF" (EWD249), Section 3 ("On The Reliability of Mechanisms"), p. 7.
1970s

Art

“APL is a mistake, carried through to perfection. It is the language of the future for the programming techniques of the past: it creates a new generation of coding bums.”

Edsger W. Dijkstra

1970s, How do we tell truths that might hurt? (1975)

Past , Future , Perfection

“When we had no computers, we had no programming problem either. When we had a few computers, we had a mild programming problem. Confronted with machines a million times as powerful, we are faced with a gigantic programming problem.”

Edsger W. Dijkstra

Dijkstra (1986) Visuals for BP's Venture Research Conference http://www.cs.utexas.edu/users/EWD/transcriptions/EWD09xx/EWD963.html (EWD 963).
1980s

Problem , Time