computer science

Knuth reward check

Knuth reward check is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Knuth reward check rather than just read about it. In short: Knuth reward checks are checks 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 highly valued in the computing community.

Key takeaways

Knuth reward check belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Knuth reward check to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Knuth reward check from memory before moving on to harder problems.

Reference excerpt

Knuth reward checks are checks 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 highly valued in the computing community.

Background

Knuth started rewarding people for discovering errors in his books after he published the first volume of The Art of Computer Programming in 1968. Initially, Knuth sent real, 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. Knuth now sends out "hexadecimal certificates" instead of negotiable checks. As of October 2001, Knuth reported having written more than 2,000 checks, with an average value exceeding $8 per check. By March 2005, the total value of the checks signed by Knuth was over $20,000. Very few of these checks were actually cashed, even the largest ones. More often they have been framed and kept as a valued keepsake.

Intelligence: Finding an error in a Knuth text. Stupidity: Cashing that $2.56 check you got.

Reward amounts In the preface of each of his books and on his website, 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. Valuable suggestions are worth 32 cents, or 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 a unique scheme inspired by the wheat and chessboard problem, starting at $2.56, and doubling every year until it reached $327.68. Recipients of this "progressive reward" reward include Chris Thompson (Cambridge) and Bogusław L. Jackowski (Gdańsk), and also Peter Breitenlohner on 20 March 1995. 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, 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.

Processing 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. When Knuth is not able to reply immediately, he adds 5% interest, compounded continuously, to the reward.

See also List of computer-related awards Erdős's problems

References

External links The Bank of San Serriffe Interview (RealVideo format) (or Transcript) with Knuth on National Public Radio

Illustrations

Worked examples

Example 1 — a first encounter with Knuth reward check

Start with the simplest possible case. Write down what Knuth reward check claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Knuth reward check before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Knuth reward check ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Knuth reward check

In research: Knuth reward check appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Knuth reward check in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Knuth reward check is common in secondary-school and first-year university syllabi. It links to neighbouring topics Challenge awards, Computer-related awards, Donald Knuth, so understanding it makes those chapters shorter.
In everyday life: Look for Knuth reward check outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Knuth reward check in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Knuth reward check means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Knuth reward check out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Knuth reward check in simple terms?

Why does Knuth reward check matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Knuth reward check?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Knuth reward check.