# Literate Programming

by Donald E. Knuth (Stanford, California: Center for the Study of Language and Information, 1992), xvi+368pp.
(CSLI Lecture Notes, no. 27.)
ISBN 0-937073-80-6
Japanese translation by Makoto Arisawa, Bungeiteki Programming (Tokyo: ASCII Corporation, 1994), 463pp.

This book is the first in a series of eight volumes that contain archival forms of my published papers, together with new material.

Literate programming is a methodology that combines a programming language with a documentation language, thereby making programs more robust, more portable, more easily maintained, and arguably more fun to write than programs that are written only in a high-level language. The main idea is to treat a program as a piece of literature, addressed to human beings rather than to a computer. The program is also viewed as a hypertext document, rather like the World Wide Web. (Indeed, I used the word WEB for this purpose long before CERN grabbed it!) This book is an anthology of essays including my early papers on related topics such as structured programming, as well as the article in The Computer Journal that launched Literate Programming itself. The articles have been revised, extended, and brought up to date.

1. Computer programming as an art [P68]
2. Structured programming with go to statements [P67]
3. A structured program to generate all topological sorting arrangements [P65]
4. Literate programming [P109]
5. Programming pearls: Sampling [Q78]
6. Programming pearls, continued: Common words [Q79]
7. How to read a WEB [from TeX: The Program]
8. Excerpts from the programs for TeX and METAFONT [from Computers & Typesetting, volumes B and D]
9. Mathematical writing [from Mathematical Writing]
10. The errors of TeX [P124]
11. The error log of TeX [P124, with new material]
12. An example of CWEB [never before published]
13. Further reading: A comprehensive bibliography of Literate Programming [never before published]

(Numbers like P68 and Q78 in this list refer to the corresponding papers in my list of publications.)

Available from the publisher (CSLI), and also from the distributor (University of Chicago Press).

This book received the Productivity Award from Computer Language magazine, 1992, awarded to products that significantly increase programmer productivity.

## Errata

For a list of corrections to errors in the first printing of this book, you may download either the errata file in plain TeX format (8812 bytes) or the errata file in DVI format (10816 bytes) or the errata file in compressed PostScript format (34478 bytes); the latter files were generated by the TeX file, and last updated 12 Jun 2004. Most of the errors in the first two printings were corrected in the third printing, but several minor errors have been found by sharp-eyed readers of the fourth printing (1998) or the fifth printing (2008) or the sixth printing (2013):

page xiii, line 8
page 19, line 11
change '1904' to '1903'
page 26, line 8 from the bottom
change '+6' to '+1'
page 26, line 5 from the bottom
change '11n+21' to '12n+19'
page 26, line 2 from the bottom
change '21%' to '14%'
page 39, line 14 from the bottom
page 44, line 5
change 'step 1 until' to 'step 1 until'
page 46, line 1
page 47, line 13 from the bottom
change 'a repeat loop' to 'a repeat loop'
page 50, line 7
change 'repeat:' to 'repeat;'
pages 51, 52, 53, 53, 56, 57
change 'integer t; value t;' to 'value t; integer t;'
page 57, line 11 from the bottom
change '$n>0$' to '$n\ge0$'
page 58, line 5
change 'average, will' to 'average will'
page 60, lines 3, 4, 5
change 'all the elements ... greater than v' to 'only elements that are less than or equal to some given value v; the right part A[j+1]...A[n] will contain only elements that are greater than or equal to v'
page 67, line 11
change 'j;' to 'j:'
page 67, line 14
change '1;' to '1; fi;'
page 74, line 24
change 'j;' to 'j:'
page 80, replace the bottom line by 6 lines
not found: $m\gets\r1$ 2 $a$
$\r4\gets1$ 1 $a$
to update$1$a$found:$\r4\gets B[\r1]$2$1-a\r4\gets\r4+1$1$1-a$update:$B[\r1]\gets\r4$2 1 page 86, line 10 change 'Eisenstadt' to 'Eisenstat' page 92, line 20 change '$\ne\{x_1,\ldots,x_k\}$which have' to '$\notin\{x_1,\ldots,x_k}$that have' page 92, line 10 from the bottom change 'integer k; value k;' to 'value k; integer k;' page 93, line 18 from the bottom change$q=y_{r-1},y_{r-2},\ldots,y_1$to$q=y_{r-1}$,$y_{r-2}$, \dots,$y_1$page 135, reference [10] this reference should be the same as [61] on page 86 page 159, line 14 add the statement 'count[0] ← 0;' (to agree with page 164) page 195, between sections 111 and 117 insert an ellipsis (three vertical dots) as between sections 16 and 95 on page 186 page 276, line 6 from the bottom change 'class L' to 'class L or class R' page 280, line 13 from the bottom change '97' to '65' page 288, line 2 from the bottom change$\theta_2$to$\theta_0$pages 294--338 (Several entries in this log have been edited for consistency of style with respect to the others) page 349, lines 9 and 10 change 'Praktis- che' to 'Prak- tische' page 354, line 8 from the bottom change 'labrea' to 'ftp.cs' page 355, line 12 change 'labrea' to 'ftp.cs' page 358, new item for the bibliography Klaus Thull, The virtual memory management of PubliC \TeX,'' {\sl TUGboat\/ \bf10},1 (April 1989), 15--22. page 361, left column change 'Macdonald' to 'MacDonald' in the Coxeter entry page 361, left column change 'x' to 'xii' in the CWEB entry page 361, right column change 'Eisenstadt, Stanley C.' to 'Eisenstat, Stanley Charles' page 362, left column Guth, Alan Harvey, 337. page 362, right column change 'Nicolass' to 'Nicolaas' in the Habermann entry page 363, right column add page 322 to the references for Frank Liang page 364, left column change 'Marneffe, Pierre-Arnoul de' to 'Marneffe, Pierre-Arnoul Frédéric Guy Donat de' page 366, left column change 'Rustin, Randall' to 'Rustin, Randall Dennis' page 366, left column Scherlis, William Louis, 322. page 367, left column change 'Thull, Klaus, 357.' to 'Thull, Klaus, 358.' page 368, left column change '139' to 'xii, 139' in the WEB entry I hope the 2013 version is otherwise error-free. But (sigh) it probably isn't. Therefore I will gratefully deposit 0x$1.00 (\$2.56) to the account of the first person who finds and reports anything that remains technically, historically, typographically, or politically incorrect. Please send suggested corrections to knuth-bug@cs.stanford.edu, or send snail mail to Prof. D. Knuth, Computer Science Department, Gates Building 4B, Stanford University, Stanford, CA 94305-9045 USA. In either case please include your postal address, so that I can mail an official certificate of deposit as a token of thanks for any improvements to which you have contributed.

I may not be able to read your message until many months have gone by, because I'm working intensively on The Art of Computer Programming. However, I promise to reply in due time.

DO NOT SEND EMAIL TO KNUTH-BUG EXCEPT TO REPORT ERRORS IN BOOKS! And if you do report an error via email, please do not include attachments of any kind; your message should be readable on brand-X operating systems for all values of X.