Editing Knuth reward check

{{Short description|Awards issued by computer scientist Donald Knuth}}
[[Image:knuth-check2.png|thumb|right|One of Donald Knuth's personally-designed reward checks, with the recipient's name and design details censored to deter forgeries]]
'''Knuth reward checks''' are [[cheque|check]]s or check-like certificates awarded by computer scientist [[Donald Knuth]] for finding technical, typographical, or historical errors, or making substantial suggestions for his publications. The ''[[MIT Technology Review]]'' describes the checks as "among computerdom's most prized trophies".<ref>Ditlea, S., "[https://www.technologyreview.com/s/400456/rewriting-the-bible-in-0s-and-1s/ Rewriting the Bible in 0's and 1's] {{Webarchive|url=https://web.archive.org/web/20181109034030/https://www.technologyreview.com/s/400456/rewriting-the-bible-in-0s-and-1s/ |date=2018-11-09 }}", ''[[MIT Technology Review]]''.</ref>

==History==
[[Image:Knuth cod.JPG|thumb|right|Bank of San Serriffe reward check]]
Knuth started rewarding people for discovering errors in his books after he published the first volume of ''[[The Art of Computer Programming]]'' in 1968.<ref name="boss">{{cite web |last1=Knuth |first1=Donald |title=Knuth: The Bank of San Serriffe |url=https://www-cs-faculty.stanford.edu/~knuth/boss.html |website=Stanford CS Faculty}}</ref>
Initially, Knuth sent real, [[Negotiable instrument|negotiable]] checks to recipients. He stopped doing so in October 2008 because of problems with check fraud. As a replacement, he started his own "Bank of San Serriffe", in the fictional nation of [[San Serriffe]], which keeps an account for everyone who found an error since 2006.<ref name="boss"></ref> Knuth now sends out "hexadecimal certificates" instead of negotiable checks.

{{As of|2001|10|alt=As of October 2001}}, Knuth reported having written more than 2,000 checks, with an average value exceeding $8 per check.<ref name="ams_fea">Donald Knuth (2002), "[https://www.ams.org/notices/200203/fea-knuth.pdf All questions answered] {{Webarchive|url=https://web.archive.org/web/20190430030346/http://www.ams.org/notices/200203/fea-knuth.pdf |date=2019-04-30 }}", ''[[Notices of the American Mathematical Society|Notices of the AMS]]'' 49(3): 318-324.</ref> {{As of|2005|alt=By March 2005}}, the total value of the checks signed by Knuth was over $20,000.<ref>David Kestenbaum, {{cite news | url=https://www.npr.org/templates/story/story.php?storyId=4532247 | date=2005-03-14 | title=NPR Interview: Donald Knuth, Founding Artist of Computer Science, at 5:42 | newspaper=NPR.org | access-date=2018-04-02 | archive-date=2018-04-03 | archive-url=https://web.archive.org/web/20180403234644/https://www.npr.org/templates/story/story.php?storyId=4532247 | url-status=live }}</ref> Very few of these checks were actually cashed, even the largest ones. More often they have been framed and kept as "bragging rights".<ref name="stanfordmag">Kara Platoni, "[http://www.stanfordalumni.org/news/magazine/2006/mayjun/features/knuth.html Love at First Byte] {{Webarchive|url=https://web.archive.org/web/20060604115901/http://www.stanfordalumni.org/news/magazine/2006/mayjun/features/knuth.html |date=2006-06-04 }}", ''Stanford Magazine'', May–June 2006</ref><ref name=history>The [http://www.tug.org/whatis.html History of TeX] {{Webarchive|url=https://web.archive.org/web/20110807163125/http://www.tug.org/whatis.html |date=2011-08-07 }}</ref>

{{cquote|Intelligence: Finding an error in a Knuth text. Stupidity: Cashing that $2.56 check you got.|||Seen in a [[Slashdot]] [[signature block|signature]], quoted by Tess O'Connor<ref>{{Cite web|url=https://www.stgray.com/quotes/programmingquotes.html|title=Programming Quotes - stgray.com|website=www.stgray.com|access-date=2021-10-17|archive-date=2021-04-17|archive-url=https://web.archive.org/web/20210417190013/http://www.stgray.com/quotes/programmingquotes.html|url-status=live}}</ref>}}

==Amount==
In the preface of each of his books and on his website,<ref>See [http://sunburn.stanford.edu/~knuth/books.html Books in Print by Donald E. Knuth] {{webarchive|url=https://web.archive.org/web/20060901073059/http://sunburn.stanford.edu/~knuth/books.html |date=2006-09-01 }}</ref> Knuth offers a reward of $2.56 ([[USD]]) to the first person to find each error in his published books, whether it be technical, typographical, or historical. Knuth explains that $2.56, or 256 cents, corresponds to one [[hexadecimal]] dollar.<ref>[http://sunburn.stanford.edu/~knuth/faq.html Frequently Asked Questions] {{webarchive|url=https://web.archive.org/web/20120210185732/http://sunburn.stanford.edu/~knuth/faq.html |date=2012-02-10 }} on [http://sunburn.stanford.edu/~knuth/ Don Knuth's webpage]   .</ref> "Valuable suggestions" are worth 32 cents, or {{frac|1|8}} the value of an error (0.2 hexadecimal dollars or 20 hexadecimal cents). In his earlier books a smaller reward was offered. For example, the 2nd edition of ''[[The Art of Computer Programming]], Volume 1'', offered $2.00.

The reward for coding errors found in Knuth's [[TeX]] and [[Metafont]] programs (as distinguished from errors in Knuth's books) followed an audacious scheme inspired by the [[wheat and chessboard problem]],<ref>{{MathWorld|title=Wheat and Chessboard Problem|urlname=WheatandChessboardProblem}}</ref> starting at $2.56, and doubling every year until it reached $327.68.<ref name="ams_fea"/> Recipients of this "sweepstakes" reward include Chris Thompson (Cambridge) and [[Bogusław L. Jackowski]] (Gdańsk),<ref>{{Cite web|url=http://www.uni-giessen.de/hrz/tex/more_info/info/mailarchiv/mutex.1995/msg00147.html|archive-url=https://web.archive.org/web/20051120141630/http://www.uni-giessen.de/hrz/tex/more_info/info/mailarchiv/mutex.1995/msg00147.html |url-status=dead |title=Installation of Knuth's 1995 release|archive-date=November 20, 2005}}</ref> and also Peter Breitenlohner on 20 March 1995.<ref>[http://www.tug.org/TUGboat/Articles/tb17-1/tb50knut.pdf TUG'95: Questions and Answers with Prof. Donald E. Knuth] {{Webarchive|url=https://web.archive.org/web/20061110181824/http://www.tug.org/TUGboat/Articles/tb17-1/tb50knut.pdf |date=2006-11-10 }} and Ch 34 of ''Digital Typography''</ref>

Each check's memo field identifies the book and page number. 1.23 indicates an error on page 23 of Volume 1. (1.23) indicates a valuable suggestion on that page. The symbol [[theta|Θ]] denotes the book ''[[Things a Computer Scientist Rarely Talks About]]'', KLR denotes the book ''Mathematical Writing'' (by Knuth, Larrabee, and Roberts), GKP and CM denote the book ''[[Concrete Mathematics]]'' (by Graham, Knuth, and Patashnik), f1 denotes fascicle 1, CMT denotes the book ''Computer Modern Typefaces'', DT denotes the book ''Digital Typography'', SN denotes ''Surreal Numbers'', CWEB denotes the book ''The CWEB System of Structured Documentation'', DA denotes the book ''Selected Papers on Design of Algorithms'', FG denotes the book ''Selected Papers on Fun and Games'', and MM denotes the book ''MMIXware - A RISC Computer for the Third Millennium''.

==Delays==
Knuth is often unable to answer immediately when a reader finds a mistake in one of his books or programs. In some cases, the delay has been several years. For example, on 1 July 1996, Knuth sent out more than 250 letters, 125 of which contained checks, for errors reported in ''[[The Art of Computer Programming]]'' since the summer of 1981. A few of these remain unclaimed as of May 2006.<ref>[https://cs.stanford.edu/~knuth/address.html What is your current mailing address?] {{Webarchive|url=https://web.archive.org/web/20180123092935/https://cs.stanford.edu/~knuth/address.html |date=2018-01-23 }} on Don Knuth's website.</ref> When Knuth is not able to reply immediately, he adds 5% interest, [[Compound interest#Continuous compounding|compounded continuously]], to the reward.

==See also==

* [[List of computer-related awards]]
* [[Paul Erdős#Erd.C5.91s.27s problems|Erdős's problems]]

==References==
{{reflist|30em}}

==External links==
*[http://www-cs-faculty.stanford.edu/~knuth/boss.html The Bank of San Serriffe]
*{{wikicite |ref=CITEREFNPR_Interview |reference=[https://www.npr.org/templates/story/story.php?storyId=4532247 Interview] ([[RealVideo]] format) (or [https://web.archive.org/web/20090421090053/http://www.soundbytes.org/phpBB2/viewtopic.php?t=5643 Transcript]) with Knuth on [[National Public Radio]]}}

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