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

Edsger Dijkstra

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Edsger Dijkstra
Age: 72 †
Born: 1930
Born: May 11
Died: 2002
Died: August 5
Computer Scientist
Engineer
Mathematician
Physicist
Scientist
University Teacher
R'dam
Edsger Dijkstra
Edsger Wybe Dijkstra
Dijkstra
EWD
E.W. Dijkstra
Never
Testing
Programming
Absence
Presence
Program
Show
Shows
Used
Bugs

More quotes by Edsger Dijkstra

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Computer science is no more about computers than astronomy is about telescopes, biology is about microscopes or chemistry is about beakers and test tubes. Science is not about tools. It is about how we use them, and what we find out when we do.
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If in physics there's something you don't understand, you can always hide behind the uncharted depths of nature. You can always blame God. You didn't make it so complex yourself. But if your program doesn't work, there is no one to hide behind. You cannot hide behind an obstinate nature. If it doesn't work, you've messed up.
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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.
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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.
Edsger Dijkstra
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I don't need to waste my time with a computer just because I am a computer scientist.
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It used to be the program's purpose to instruct our computers it became the computer's purpose to execute our programs.
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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.
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I mentioned the non-competitive spirit explicitly, because these days, excellence is a fashionable concept. But excellence is a competitive notion, and that is not what we are heading for: we are heading for perfection.
Edsger Dijkstra
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Don't compete with me: firstly, I have more experience, and secondly, I have chosen the weapons.
Edsger Dijkstra
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Progress is possible only if we train ourselves to think about programs without thinking of them as pieces of executable code.
Edsger Dijkstra
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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 Dijkstra
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We shall do a much better programming job, provided that we approach the task with a full appreciation of its tremendous difficulty, provided that we stick to modest and elegant programming languages, provided that we respect the intrinsic limitations of the human mind and approach the task as Very Humble Programmers.
Edsger Dijkstra
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There is very little point in trying to urge the world to mend its ways as long as that world is still convinced that its ways are perfectly adequate.
Edsger Dijkstra
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The problems of the real world are primarily those you are left with when you refuse to apply their effective solutions.
Edsger Dijkstra
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... as a slow-witted human being I have a very small head and I had better learn to live with it and to respect my limitations and give them full credit, rather than to try to ignore them, for the latter vain effort will be punished by failure.
Edsger Dijkstra
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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 Dijkstra
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Object-oriented programming is an exceptionally bad idea which could only have originated in California.
Edsger Dijkstra
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It is a mistake to think that programmers wares are programs. Programmers have to produce trustworthy solutions and present it in the form of cogent arguments. Programs source code is just the accompanying material to which these arguments are to be applied to.
Edsger Dijkstra
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Testing shows the presence, not the absence of bugs.
Edsger Dijkstra
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Programming is one of the most difficult branches of applied mathematics the poorer mathematicians had better remain pure mathematicians.
Edsger Dijkstra