Knuth reward check

From Wikipedia, the free encyclopedia

One of Donald Knuth's reward checks

In the preface of each of his books and on his website,^[1] computer scientist Donald Knuth offers to cheerfully pay a reward of $2.56 (USD) to the first finder of each error in one of his published books, whether it be technical, typographical, or historical. Knuth explains that $2.56, or 256 cents, corresponds to one hexadecimal dollar.^[2] Valuable suggestions are worth 32¢.

These reward checks have been described as "among computerdom's most prized trophies".^[3] As of October 2001, Knuth reports having written more than 2,000 such checks, with an average value exceeding $8 per check.^[4] As of March 2005, the total value of the checks signed by Knuth was over $20,000 (see NPR interview below). Very few of these checks are actually cashed, however, even the largest ones; more often, they are framed, or kept as bragging rights.^[5]^[6]

A check for $10.24, after finding 4 corrections in The Art of Computer Programming

Intelligence: Finding an error in a Knuth text.

Stupidity: Cashing that $2.56 check you got.

Seen in a Slashdot signature, quoted by Edward O'Connor^[7]

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.^[8] It started at $2.56, and doubled every year until it reached $327.68.^[4] Recipients of this "sweepstakes" reward include Chris Thompson (Cambridge) and Boguslaw Jackowski (Gdansk),^[9] and also Peter Breitenlohner on 20 March 1995.^[10]

Knuth is often not able 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 long. 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.^[11] When Knuth is not able to reply immediately, he adds 5% interest, compounded continuously, to the reward.^[12]

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 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, and SN denotes Surreal Numbers.

[edit] Criticism

Knuth has created [TeX], which aims to 'allow anybody to produce high-quality books using a reasonable amount of effort'. Knuth does not mention usability bugs in his selection criteria to award the cheque, nor have any usability bugs been filed for his software. TeX's current usage is mainly limited to computer scientists, mathematicians and physicists, and there have been frequent complaints about the obscurity of the format, editing tools, and font system.

However unlike regular software, no bug reports have ever been filed to improve usability in Knuth's programs, thus artificially limiting the amount given in the cheque.