Sourced

• Beware of bugs in the above code; I have only proved it correct, not tried it.
  • Donald Knuth's webpage states the line was used to end a memo entitled Notes on the van Emde Boas construction of priority deques: An instructive use of recursion (1977)

• I can’t be as confident about computer science as I can about biology. Biology easily has 500 years of exciting problems to work on. It’s at that level.
  • Computer Literacy Bookshops Interview Computer Literacy Bookshops Interview (1993)
    • On why bioinformatics is very exciting

• The psychological profiling [of a programmer] is mostly the ability to shift levels of abstraction, from low level to high level. To see something in the small and to see something in the large.
  • Jack Woehr. An interview with Donald Knuth. Dr. Dobb's Journal, pages 16-22 (April 1996)

• The important thing, once you have enough to eat and a nice house, is what you can do for others, what you can contribute to the enterprise as a whole.
  • Jack Woehr. An interview with Donald Knuth. Dr. Dobb's Journal, pages 16-22 (April 1996)

• The whole thing that makes a mathematician’s life worthwhile is that he gets the grudging admiration of three or four colleagues.
  • Jack Woehr. An interview with Donald Knuth. Dr. Dobb's Journal, pages 16-22 (April 1996)

• Science is what we understand well enough to explain to a computer. Art is everything else we do.
  • Foreword to the book A=B (1996)

• A mathematical formula should never be "owned" by anybody! Mathematics belong to God.
  • Digital Typography, ch. 1, p. 8 (1999)

• I define UNIX as 30 definitions of regular expressions living under one roof.
  • Digital Typography, ch. 33, p. 649 (1999)

• I can’t go to a restaurant and order food because I keep looking at the fonts on the menu.

• Email is a wonderful thing for people whose role in life is to be on top of things. But not for me; my role is to be on the bottom of things. What I do takes long hours of studying and uninterruptible concentration.
  • Knuth versus Email

The Art of Computer Programming (1968-2005)

• An algorithm must be seen to be believed.
  • Vol. I, Fundamental Algorithms, Section 1.1 (1968)

• The sun comes up just about as often as it goes down, in the long run, but this doesn't make its motion random.
  • Vol. II, Seminumerical Algorithms, Section 3.3.2 part B, first paragraph (1969)

• The reason is not to glorify "bit chasing"; a more fundamental issue is at stake here: Numerical subroutines should deliver results that satisfy simple, useful mathematical laws whenever possible. [...] Without any underlying symmetry properties, the job of proving interesting results becomes extremely unpleasant. The enjoyment of one's tools is an essential ingredient of successful work.
  • Vol. II, Seminumerical Algorithms, Section 4.2.2 part A, final paragraph [Italics in source]

• Any inaccuracies in this index may be explained by the fact that it has been sorted with the help of a computer.
  • Vol. III, Sorting and Searching, End of index (1973)

• Science is knowledge which we understand so well that we can teach it to a computer; and if we don't fully understand something, it is an art to deal with it.
  • p. 668

• We should continually be striving to transform every art into a science: in the process, we advance the art.
  • p. 669 [italics in source]

• Premature optimization is the root of all evil (or at least most of it) in programming.
  • p. 671
  • Premature optimization is the root of all evil.
    • Variant in Knuth, "Structured Programming with Goto Statements". Computing Surveys 6:4 (December 1974), pp. 261–301, §1.
  • Knuth refers to this as "Hoare's Dictum" 15 years later in "The Errors of Tex", Software—Practice & Experience 19:7 (July 1989), pp. 607–685. However, the attribution to C. A. R. Hoare is doubtful.http://shreevatsa.wordpress.com/2008/05/16/premature-optimization-is-the-root-of-all-evil/
    • All three of these papers are reprinted in Knuth, Literate Programming, 1992, Center for the Study of Language and Information ISBN 0937073806

• Computer programming is an art, because it applies accumulated knowledge to the world, because it requires skill and ingenuity, and especially because it produces objects of beauty. A programmer who subconsciously views himself as an artist will enjoy what he does and will do it better.
  • p. 673

Quotes about

• For his major contributions to the analysis of algorithms and the design of programming languages, and in particular for his contributions to the "art of computer programming" through his well-known books in a continuous series by this title.
  • 1974 Turing Award Citationhttp://awards.acm.org/citation.cfm?id=7143252&srt=all&aw=140&ao=AMTURING