Edsger W. Dijkstra

Quotes are arranged in chronological order

For a number of years I have been familiar with the observation that the quality of programmers is a decreasing function of the density of go to statements in the programs they produce. More recently I discovered why the use of the go to statement has such disastrous effects, and I became convinced that the go to statement should be abolished from all "higher level" programming languages.

— Edsger W. Dijkstra men

Our intellectual powers are rather geared to master static relations and that our powers toprocesses 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 war

Testing shows the presence, not the absence of bugs

— Edsger W. Dijkstra

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

— Edsger W. Dijkstra

A convincing demonstration of correctness being impossible as long as the mechanism is regarded as a black box, our only hope lies in not regarding the mechanism as a black box.

— Edsger W. Dijkstra hope

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 man

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 war

On Our Inability To Do Much.

— Edsger W. Dijkstra

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 religion

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 age

Several people have told me that my inability to suffer fools gladly is one of my main weaknesses.

— Edsger W. Dijkstra people

Write a paper promising salvation, make it a 'structured' something or a 'virtual' something, or 'abstract', 'distributed' or 'higher-order' or 'applicative' and you can almost be certain of having started a new cult.

— Edsger W. Dijkstra art

For me, the first challenge for computing science is to discover how to maintain order in a finite, but very large, discrete universe that is intricately intertwined. And a second, but not less important challenge is how to mould what you have achieved in solving the first problem, into a teachable discipline: it does not suffice to hone your own intellect (that will join you in your grave), you must teach others how to hone theirs. The more you concentrate on these two challenges, the clearer you will see that they are only two sides of the same coin: teaching yourself is discovering what is teachable.

— Edsger W. Dijkstra science

1972Lecture,15 (10), October 1972: pp. 859–866

— Edsger W. Dijkstra

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 man

We must be very careful when we give advice to younger people: sometimes they follow it!

— Edsger W. Dijkstra time

The major cause [of the software crisis] is that the machines have become several orders of magnitude more powerful! To put it quite bluntly: as long as there were no machines, programming was no problem at all; when we had a few weak computers, programming became a mild problem, and now we have gigantic computers, programming has become an equally gigantic problem. In this sense the electronic industry has not solved a single problem, it has only created them, it has created the problem of using its products.

— Edsger W. Dijkstra war

FORTRAN's tragic fate has been its wide acceptance, mentally chaining thousands and thousands of programmers to our past mistakes.

— Edsger W. Dijkstra men

LISP has been jokingly described as "the most intelligent way to misuse a computer". I think that description a great compliment because it transmits the full flavor of liberation: it has assisted a number of our most gifted fellow humans in thinking previously impossible thoughts.

— Edsger W. Dijkstra men

When FORTRAN has been called an infantile disorder, full PL/1, with its growth characteristics of a dangerous tumor, could turn out to be a fatal disease.

— Edsger W. Dijkstra growth

If you want more effective programmers, you will discover that they should not waste their time debugging, they should not introduce the bugs to start with.

— Edsger W. Dijkstra time

Program testing can be a very effective way to show the presence of bugs, but it is hopelessly inadequate for showing their absence.

— Edsger W. Dijkstra hope

The effective exploitation of his powers of abstraction must be regarded as one of the most vital activities of a competent programmer.

— Edsger W. Dijkstra power

(numbered EWD498, written ) was written as a series of , and is the source of several popular quotations. It was also published in Selected Writings on Computing:A Personal Perspective.

— Edsger W. Dijkstra writing

The use of COBOL cripples the mind; its teaching should, therefore, be regarded as a criminal offense.

— Edsger W. Dijkstra mind

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 future

, 'the infantile disorder', by now nearly 20 years old, is hopelessly inadequate for whatever computer application you have in mind today: it is now too clumsy, too risky, and too expensive to use.

— Edsger W. Dijkstra hope

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

— Edsger W. Dijkstra men

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

— Edsger W. Dijkstra hope

Besides a mathematical inclination, an exceptionally good mastery of one's native tongue is the most vital asset of a competent programmer.

— Edsger W. Dijkstra good

Simplicity is prerequisite for reliability.

— Edsger W. Dijkstra city

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

— Edsger W. Dijkstra poor

We can found no scientific discipline, nor a hearty profession, on the technical mistakes of the Department of Defense and, mainly, one computer manufacturer.

— Edsger W. Dijkstra art

About the use of language: it is impossible to sharpen a pencil with a blunt axe. It is equally vain to try to do it with ten blunt axes instead.

— Edsger W. Dijkstra language

Thank goodness we don't have only serious problems, but ridiculous ones as well.

— Edsger W. Dijkstra good

[Thoughis a fairly new discipline, it is predominantly based on the Cartesian . As Edsgar W. Dijkstra has pointed out] A scientific discipline emerges with the - usually rather slow! - discovery of which aspects can be meaningfully 'studied in isolation for the sake of their own consistency.

— Edsger W. Dijkstra art

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 success

I think of the company advertising "Thought Processors" or the college pretending that learningsuffices or at least helps, whereas the teaching of BASIC should be rated as a criminal offence: it mutilates the mind beyond recovery.

— Edsger W. Dijkstra mind

The question of whether Machines Can Think... is about as relevant as the question of whether Submarines Can Swim.

— Edsger W. Dijkstra think

Simplicity is a great virtue but it requires hard work to achieve it and education to appreciate it. And to make matters worse: complexity sells better.

— Edsger W. Dijkstra education

Probably I am very naive, but I also think I prefer to remain so, at least for the time being and perhaps for the rest of my life.

— Edsger W. Dijkstra life

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 time

The problems of the real world are primarily those you are left with when you refuse to apply their effective solutions.

— Edsger W. Dijkstra world

When I came back from Munich, it was September, and I was Professor of Mathematics at the Eindhoven University of Technology. Later I learned that I had been the Department's third choice, after two numerical analysts had turned the invitation down; the decision to invite me had not been an easy one, on the one hand because I had not really studied mathematics, and on the other hand because of my sandals, my beard and my "arrogance" (whatever that may be).

— Edsger W. Dijkstra art

I mean, if 10 years from now, when you are doing something quick and dirty, you suddenly visualize that I am looking over your shoulders and say to yourself "Dijkstra would not have liked this", well, that would be enough immortality for me.

— Edsger W. Dijkstra self

Elegance is not a dispensable luxury but a quality that decides between success and failure.

— Edsger W. Dijkstra success

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 ofgurus.

— Edsger W. Dijkstra war

It is not the task of the University to offer what society asks for, but to give what society needs.

— Edsger W. Dijkstra society

There are many different styles of composition. I characterize them always as Mozart versus Beethoven. When Mozart began to write at that time he had the composition ready in his mind. He wrote the manuscript and it was 'aus einem Guss' (casted as one). And it was also written very beautiful. Beethoven was an indecisive and a tinkerer and wrote down before he had the composition ready and plastered parts over to change them. There was a certain place where he plastered over nine times and one did remove that carefully to see what happened and it turned out the last version was the same as the first one.

— Edsger W. Dijkstra time

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