What's your favourite quote about programming?
One quote per answer, and please check for duplicates before posting!
It always takes longer than you expect, even when you take into account Hofstadter's Law.
— Hofstadter's Law
Nine people can't make a baby in a month.
— Fred Brooks, The Mythical Man-Month
We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil. Yet we should not pass up our opportunities in that critical 3%.
— Donald Knuth, Structured Programming with go to Statements, JACM Computing Surveys, Vol 6, No. 4, Dec. 1974, p.268
This is extracted from the below two paragraphs, which not only say why he comes to the above conclusion, but gives information on how to avoid this mistake:
There is no doubt that the grail of efficiency leads to abuse. Programmers waste enormous amounts of time thinking about, or worrying about, the speed of noncritical parts of their programs, and these attempts at efficiency actually have a strong negative impact when debugging and maintenance are considered. We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil.
Yet we should not pass up our opportunities in that critical 3%. A good programmer will not be lulled into complacency by such reasoning, he will be wise to look carefully at the critical code; but only after that code has been identified. It is often a mistake to make a priori judgments about what parts of a program are really critical, since the universal experience of programmers who have been using measurement tools has been that their intuitive guesses fail. (…)
The first 90% of the code accounts for the first 90% of the development time. The remaining 10% of the code accounts for the other 90% of the development time.
On two occasions I have been asked, "Pray, Mr. Babbage, if you put into the machine wrong figures, will the right answers come out?" In one case a member of the Upper, and in the other a member of the Lower House put this question. I am not able rightly to apprehend the kind of confusion of ideas that could provoke such a question.
— Charles Babbage
Arguably the first documented case of a programmer encountering stupid user questions.
Il semble que la perfection soit atteinte non quand il n'y a plus rien à ajouter, mais quand il n'y a plus rien à retrancher.
— Antoine de Saint-Exupéry, French writer (1900-1944), Terre des Hommes (1939)
(It would seem that perfection is attained not when there is nothing left to add, but when there is nothing left to take away.)
— Chris Heilmann
Given a large enough beta-tester and co-developer base, almost every problem will be characterized quickly and the fix obvious to someone.
Or, less formally,
Given enough eyeballs, all bugs are shallow.