View source for TeX

{{short description|Typesetting system}}
{{other uses|Tex (disambiguation)}}
{{Use dmy dates|date=January 2021}}
{{Infobox software
| name                   = TeX
| logo                   = TeX logo.svg{{!}}class=skin-invert
| logo_size              = 
| developer              = [[Donald Knuth]]
| released               = {{start date and age|df=yes|1978}}
| latest_release_version = TeX Live 2024<ref name="texlive">{{cite web |title=TeX Live - TeX Users Group |url=https://tug.org/texlive/ |website=tug.org |access-date=25 April 2024}}</ref>
| latest_release_date    = {{start date and age|df=yes|2024|3|13}}
| latest preview version = 
| latest preview date    = <!--  {{Start date and age|df=yes|YYYY|MM|DD}} -->
| operating_system       = [[Cross-platform]]
| genre                  = [[Typesetting]]
| programming_language   = [[WEB]]/[[Pascal (programming language)|Pascal]]
| license                = [[Permissive free software license|Permissive free software]]
| website                = {{url|https://tug.org/}}
}}
{{Infobox file format
| name                   = TeX
| icon                   =
| logo                   =
| screenshot             =
| caption                =
| extension              = .tex
| mime                   = application/x-tex{{Efn|name=Unreg|[[Media type#Unregistered tree|Unregistered media type]]}}
| type code              =
| uniform type           =
| magic                  =
| owner                  =
| released               = {{Start date and age|1978|df=yes}}
| latest release version =
| latest release date    =
| genre                  = [[Document file format]]
| container for          =
| contained by           =
| extended from          =
| extended to            =
| standard               =
| url                    =
}}

'''TeX'''  ({{IPAc-en|t|ɛ|x}}, see [[#Pronunciation and spelling|below]]), stylized within the system as {{Stylized LaTeX|tex}}, is a [[typesetting]] [[Computer program|program]] which was designed and written by computer scientist and Stanford University professor [[Donald Knuth]]<ref>{{cite web |url= https://gcc.gnu.org/ml/java/1999-q2/msg00419.html |title=Per Bothner (attendee at TeX Project meetings) discusses authorship |quote= Knuth definitely wrote most of the code himself, at least for the Metafont re-write, for which I have pe[r]sonal knowledge.  However, some of his students (such as Michael Plass and John Hobby) did work on the algorithms used in TeX and Metafont.}}</ref> and first released in 1978. The term now refers to the system of extensions – which includes software programs called TeX ''engines'', sets of TeX [[Macro (computer science)|macros]], and packages which provide extra typesetting functionality – built around the original TeX language.  TeX is a popular means of typesetting complex [[mathematical formulae]]; it has been noted as one of the most sophisticated digital [[Typography|typographical]] systems.<ref>Yannis Haralambous. ''Fonts & Encodings (Translated by P. Scott Horne)''. Beijing; Sebastopol, Calif: O'Reilly Media, 2007, pp. 235.</ref>

TeX is widely used in [[academia]], especially in [[mathematics]], [[computer science]], [[economics]], [[political science]], [[engineering]], [[linguistics]], [[physics]], [[statistics]], and [[quantitative psychology]]. It has long since displaced [[troff|Unix troff]],{{efn|Although ''troff'' still remains as the default formatter of the UNIX documentation.}} the previously favoured formatting system, in most [[Unix]] installations. It is also used for many other typesetting tasks, especially in the form of [[LaTeX]], [[ConTeXt]], and other [[Macro (computer science)|macro]] packages.

TeX was designed with two main goals in mind: to allow anybody to produce high-quality books with minimal effort, and to provide a system that would give exactly the same results on all computers, at any point in time (together with the [[Metafont]] language for [[font]] description and the [[Computer Modern]] family of [[typeface]]s).<ref>{{cite journal | last=Gaudeul | first=Alexia | title=Do Open Source Developers Respond to Competition?: The (La)TeX Case Study | journal=SSRN Electronic Journal | date=2006 | issn=1556-5068 | doi=10.2139/ssrn.908946 | doi-access=free }}</ref> TeX is [[free software]], which made it accessible to a wide range of users.

==History==

When the first paper volume of Knuth's ''[[The Art of Computer Programming]]'' was published in 1968,<ref>{{cite web|url=http://www-cs-faculty.stanford.edu/~uno/vita.html|title=Less brief biography|last1=Knuth|first1=Donald E|website=Don Knuth's Home Page|access-date=9 January 2017|archive-date=5 December 2016|archive-url=https://web.archive.org/web/20161205093445/http://www-cs-faculty.stanford.edu/~uno/vita.html|url-status=dead}}</ref> it was typeset using [[hot metal typesetting]] on a [[Monotype system|Monotype machine]]. This method, dating back to the 19th century, produced a "classic style" appreciated by Knuth.<ref name="Knuth Kyoto 1996">{{cite web|url=https://www.kyotoprize.org/wp/wp-content/uploads/2016/02/12kA_lct_EN.pdf|archive-url=https://web.archive.org/web/20180127194502/http://www.kyotoprize.org/wp/wp-content/uploads/2016/02/12kA_lct_EN.pdf|url-status=dead|archive-date=27 January 2018|title=Commemorative lecture of the Kyoto Prize, 1996|last1=Knuth |first1=Donald E|publisher=[[Kyoto Prize]]|access-date=18 August 2018}}</ref> When the second edition was published, in 1976, the whole book had to be typeset again because the Monotype technology had been largely replaced by [[phototypesetting]], and the original [[Font|fonts]] were no longer available. When Knuth received the [[galley proof]]s of the new book on 30 March 1977, he found them inferior. Disappointed, Knuth set out to design his own typesetting system.

Knuth saw for the first time the output of a high-quality digital typesetting system, and became interested in digital typography. On 13 May 1977, he wrote a memo to himself describing the basic features of TeX.<ref>{{Citation | first = Donald Ervin | last = Knuth | url = https://www.saildart.org/TEXDR.AFT&#91;1,DEK&#93;1 | archive-url = https://web.archive.org/web/20150112075949/https://www.saildart.org/TEXDR.AFT%5B1%2CDEK%5D1#91;1,DEK&#93;1 | url-status = dead | archive-date = 2015-01-12 | title = TEXDR.AFT }}</ref> He planned to finish it on his [[sabbatical]] in 1978, but as it happened, the language was not "[[Freeze (software engineering)|frozen]]" (ready to use) until 1989, more than ten years later. [[Guy L. Steele, Jr.|Guy Steele]] happened to be at [[Stanford University|Stanford]] during the summer of 1978, when Knuth was developing his first version of TeX. When Steele returned to the [[Massachusetts Institute of Technology]] that autumn, he rewrote TeX's input/output ([[I/O]]) to run under the [[Incompatible Timesharing System]] (ITS) operating system. The first version of TeX, called TeX78, was written in the [[SAIL programming language]] to run on a [[PDP-10]] under Stanford's [[WAITS]] operating system.<ref>{{FOLDOC|TeX}}</ref>

=== WEB and literate programming ===
For later versions of TeX, Knuth invented the concept of [[literate programming]], a way of producing compilable [[source code]] and cross-linked documentation typeset in TeX from the same original file. The language used is called [[WEB]] and produces programs in DEC PDP-10 [[Pascal programming language|Pascal]].

=== TeX82 ===
TeX82, a new version of TeX rewritten from scratch, was published in 1982. Among other changes, the original [[hyphenation algorithm]] was replaced by a new algorithm written by [[Frank Liang]]. TeX82 also uses [[fixed-point arithmetic]] instead of [[floating-point arithmetic|floating-point]], to ensure reproducibility of the results across different computer hardware,{{sfn|Knuth|Plass|1981|p=144}} and includes a real, [[Turing completeness|Turing-complete]] programming language, following intense lobbying by Guy Steele.<ref>Knuth, Donald E. ''[http://maps.aanhet.net/maps/pdf/16_15.pdf Knuth meets NTG members]'', NTG: MAPS. '''16''' (1996), 38–49. Reprinted as ''Questions and Answers, III'', chapter 33 of ''Digital Typography'', p. 648.</ref> In 1989, Donald Knuth released new versions of TeX and [[Metafont]].<ref>Knuth, Donald E. [http://www.tug.org/TUGboat/Articles/tb10-3/tb25knut.pdf ''The New Versions of TeX and METAFONT''], TUGboat '''10''' (1989), 325–328; '''11''' (1990), 12. Reprinted as chapter 29 of ''Digital Typography''.</ref> Despite his desire to keep the program stable, Knuth realized that 128&nbsp;different characters for the text input were not enough to accommodate foreign languages; the main change in version 3.0 of TeX is thus the ability to work with [[8-bit]] inputs, allowing 256 different characters in the text input. TeX3.0 was released on March 15, 1990.<ref>{{Cite book |last=Hoenig |first=Alan |url=https://books.google.com/books?id=-xzeQtE4y0kC&dq=TeX82+published+in+1982&pg=PA8 |title=TeX Unbound: LaTeX & TeX Strategies for Fonts, Graphics, & More |date=1998 |publisher=Oxford University Press |isbn=978-0-19-509686-6 |language=en}}</ref>

Since version 3, TeX has used an idiosyncratic [[software versioning|version numbering system]], where updates have been indicated by adding an extra digit at the end of the decimal, so that the version number [[asymptotically]] approaches [[Pi|{{pi}}]]. This is a reflection of the fact that TeX is now very stable, and only minor updates are anticipated. The current version of TeX is 3.141592653; it was last updated in 2021.<ref>{{cite web|title=TeX 21 release|url=http://ftp.cs.stanford.edu/pub/tex/tex21.tar.gz|access-date=2022-01-05}}</ref> The design was frozen after version 3.0, and no new feature or fundamental change will be added, so all newer versions will contain only [[Software bug|bug]] fixes.<ref name=":1">{{Cite web|url=https://texfaq.org/FAQ-TeXfuture|title=What is the future of TeX?|date=2018-05-27|website=The TeX FAQ|access-date=2019-07-21|archive-date=28 April 2019|archive-url=https://web.archive.org/web/20190428184722/https://texfaq.org/FAQ-TeXfuture|url-status=dead}}</ref> Even though Donald Knuth himself has suggested a few areas in which TeX could have been improved, he indicated that he firmly believes that having an unchanged system that will produce the same output now and in the future is more important than introducing new features. For this reason, he has stated that the "absolutely final change (to be made after my death)" will be to change the version number to {{pi}}, at which point all remaining bugs will become features.<ref>Knuth, Donald E. [http://www.ntg.nl/maps/05/34.pdf ''The future of TeX and METAFONT''], NTG journal MAPS (1990), 489. Reprinted as chapter 30 of ''Digital Typography'', p. 571.</ref> Likewise, versions of Metafont after 2.0 asymptotically approach {{Mvar|[[E (mathematical constant)|e]]}} (currently at 2.7182818), and a similar change will be applied after Knuth's death.<ref name=":1" />

=== Public domain ===
Since the source code of TeX is essentially in the [[public domain]] (see below), other programmers are allowed (and explicitly encouraged) to improve the system, but are required to use another name to distribute the modified TeX, meaning that the [[source code]] can still evolve. For example, the [[Omega (TeX)|Omega]] project was developed after 1991, primarily to enhance TeX's multilingual typesetting abilities.<ref>{{Cite web|url=https://texfaq.org/FAQ-enginedev|title=TeX Engine development|date=2018-05-24|website=The TeX FAQ|access-date=2019-07-21|archive-date=28 April 2019|archive-url=https://web.archive.org/web/20190428184859/https://texfaq.org/FAQ-enginedev|url-status=dead}}</ref> Knuth created "unofficial" modified versions, such as [[TeX-XeT]], which allows a user to mix texts written in [[Bi-directional text|left-to-right and right-to-left]] [[writing system]]s in the same document.<ref name="autogenerated1"/>

==Use of TeX==
In several technical fields such as computer science, mathematics, engineering and physics, TeX has become a [[de facto standard]]. Many thousands of books have been published using TeX, including books published by [[Addison-Wesley]], [[Cambridge University Press]], [[Elsevier]], [[Oxford University Press]], and [[Springer Science+Business Media|Springer]]. Numerous journals in these fields are produced using TeX or LaTeX, allowing authors to submit their raw manuscript written in TeX.{{sfn|Beebe|2004|p=10}} While many publications in other fields, including dictionaries and legal publications, have been produced using TeX, it has not been as successful as in the more technical fields, as TeX was primarily designed to typeset mathematics.

When he designed TeX, Donald Knuth did not believe that a single typesetting system would fit everyone's needs; instead, he designed many hooks inside the program so that it would be possible to write extensions, and released the source code, hoping that the publishers would design versions tailoring to their own needs. While such extensions have been created (including some by Knuth himself),<ref name="autogenerated1">{{Citation|last1=Knuth|first1=Donald E |title=Mixing Right-to-Left Texts with Left-to-Right Texts|date=1987 |url=http://www.tug.org/TUGboat/Articles/tb08-1/tb17knutmix.pdf|journal=TUGboat|volume=8|pages=14–25 |last2=MacKay|first2=Pierre}}.</ref> most people have extended TeX only using macros and it has remained a system associated with technical typesetting.<ref>{{Citation|last=Knuth|first=Donald E|title=Questions and Answers I|date=1996|journal=TUGboat |volume=17 |pages=7–22}}.</ref><ref>{{Citation|last=Knuth |first=Donald E|title=Questions and Answers II|date=1996|journal=TUGboat|volume=17|pages=355–367}}. </ref><ref name="DigitalTypography"/>

==Typesetting system==
TeX commands commonly start with a [[backslash]] and are grouped with [[Bracket|curly braces]]. Almost all of TeX's syntactic properties can be changed on the fly, which makes TeX input hard to parse by anything but TeX itself. TeX is a [[Macro (computer science)|macro]]- and [[token (parser)|token]]-based language: many commands, including most user-defined ones, are expanded on the fly until only unexpandable tokens remain, which are then executed. Expansion itself is practically free from side effects. [[Tail recursion]] of macros takes no memory, and if-then-else constructs are available. This makes TeX a [[Turing completeness|Turing-complete]] language even at the expansion level.<ref>{{Citation | first = Alan | last = Jeffrey | url = http://tug.org/TUGboat/Articles/tb11-2/tb28jeffrey.pdf | title = Lists in TeX's Mouth | journal = TUGboat | volume = 11 | number = 2 | date = 1990 | pages = 237–45}}</ref> The system can be divided into four levels: in the first, characters are read from the input file and assigned a category code (sometimes called "catcode", for short). Combinations of a backslash (actually, any character of category zero) followed by letters (characters of category 11) or a single other character are replaced by a control-sequence token. In this sense, this stage is like lexical analysis, although it does not form numbers from digits. In the next stage, expandable control sequences (such as conditionals or defined macros) are replaced by their replacement text. The input for the third stage is then a stream of characters (including the ones with special meaning) and unexpandable control sequences (typically assignments and visual commands). Here, the characters get assembled into a paragraph, and TeX's paragraph breaking algorithm works by optimizing breakpoints over the whole paragraph. The fourth stage breaks the vertical list of lines and other material into pages.

The TeX system has precise knowledge of the sizes of all characters and symbols, and using this information, it computes the optimal arrangement of letters per line and lines per page. It then produces a [[DVI file format|DVI]] file ("DeVice Independent") containing the final locations of all characters. This DVI file can then be printed directly given an appropriate printer driver, or it can be converted to other formats. Nowadays, [[pdfTeX]] is often used, which bypasses DVI generation altogether.<ref>{{Cite web|url=https://ctan.org/pkg/pdftex?lang=en|title=CTAN: Package pdftex|website=ctan.org|access-date=2019-07-21}}</ref> The base TeX system understands about 300 commands, called ''primitives''.{{Sfn|Knuth|1984|p=9}} These low-level commands are rarely used directly by users, and most functionality is provided by format files (predumped memory images of TeX after large macro collections have been loaded). Knuth's original default format, which adds about 600 commands, is Plain TeX.<ref>{{citation | title = Plain TeX | type = source code | url = ftp://tug.ctan.org/pub/tex-archive/systems/knuth/dist/lib/plain.tex | publisher = CTAN}}</ref> The most widely used format is [[LaTeX]], originally developed by [[Leslie Lamport]], which incorporates document styles for books, letters, slides, etc., and adds support for referencing and automatic numbering of sections and equations. Another widely used format, [[AMS-TeX]], is produced by the [[American Mathematical Society]] and provides many more user-friendly commands, which can be altered by journals to fit with their house style. Most of the features of AMS-TeX can be used in LaTeX by using the "AMS packages" (e.g., <code>amsmath</code>, <code>amssymb</code>) and the "AMS document classes" (e.g., <code>amsart</code>, <code>amsbook</code>). This is then referred to as [[AMS-LaTeX]].<ref>{{Cite web|url=https://texfaq.org/FAQ-AMSpkg|title=What are the AMS packages (amsmath, etc.)?|date=2018-05-27|website=The TeX FAQ|access-date=2019-07-21|archive-date=28 April 2019|archive-url=https://web.archive.org/web/20190428184756/https://texfaq.org/FAQ-AMSpkg|url-status=dead}}</ref> Other formats include [[ConTeXt]], used primarily for desktop publishing and written mostly by Hans Hagen at [[PRAGMA Advanced Document Engineering|Pragma]].

===How it is run===
[[File:LaTeX sample.png|thumb|A sample page produced using TeX with the [[LaTeX]] macros]]
A sample [[Hello world program]] in plain TeX is:

<syntaxhighlight lang="latex">
Hello, World
\bye          % marks the end of the file; not shown in the final output
</syntaxhighlight>

This might be in a file ''myfile.tex'', as ''.tex'' is a common [[file extension]] for plain TeX files. By default, everything that follows a percent sign on a line is a comment, ignored by TeX. Running TeX on this file (for example, by typing <kbd>tex&nbsp;myfile.tex</kbd> in a [[command-line interpreter]], or by calling it from a [[graphical user interface]]) will create an output file called ''myfile.dvi'', representing the content of the page in a '''d'''e'''v'''ice '''i'''ndependent format (DVI). A DVI file could then be either viewed on screen or converted to a suitable format for any of the various printers for which a device driver existed (printer support was generally not an operating system feature at the time that TeX was created). Knuth has said that there is nothing inherent in TeX that requires DVI as the output format, and later versions of TeX, notably pdfTeX, XeTeX, and LuaTeX, all support output directly to [[Portable Document Format|PDF]].

===Mathematical example===
{{Anchor|math mode|mathematics mode|mathematical mode}}

TeX provides a different text syntax specifically for mathematical formulas. For example, the [[quadratic formula]] (which is the solution of the [[quadratic equation]]) appears as:

{|
! Source code !! Renders as
|-
|<syntaxhighlight lang="latex">
The quadratic formula is $-b \pm \sqrt{b^2 - 4ac} \over 2a$
\bye
</syntaxhighlight>
|<math>\hbox{The quadratic formula is } \textstyle{-b \pm \sqrt{b^2 - 4ac} \over 2a}</math>
|}

The formula is printed in a way a person would write by hand, or typeset the equation. In a document, entering ''mathematics mode'' is done by starting with a $ symbol, then entering a formula in TeX syntax, and closing again with another of the same symbol. Knuth explained in jest that he chose the dollar sign to indicate the beginning and end of mathematical mode in plain TeX because typesetting mathematics was traditionally supposed to be expensive.{{Sfn | Knuth | 1984 | loc = Ch. 16: Typing Math Formulas | p = 127}} ''Display mathematics'' (mathematics presented centred on a new line) is similar but uses $$ instead of a single $ symbol. For example, the above with the quadratic formula in display math:

{|
! Source code !! Renders as
|-
|<syntaxhighlight lang="latex">
The quadratic formula is $$-b \pm \sqrt{b^2 - 4ac} \over 2a$$
\bye
</syntaxhighlight>
|<math>\begin{matrix} \text{The quadratic formula is} \\  \displaystyle{\frac{-b \pm \sqrt{b^2 - 4ac}}{2a}} \end{matrix}</math>
|}

(The examples here are not actually rendered with TeX; spacing, character sizes, and all else may differ.)

==Aspects==
The TeX software incorporates several aspects that were not available, or were of lower quality, in other typesetting programs at the time when TeX was released. Some of the innovations are based on interesting algorithms, and have led to several theses for Knuth's students. While some of these discoveries have now been incorporated into other typesetting programs, others, such as the rules for mathematical spacing, are still unique.

===Mathematical spacing===
[[File:AMS Euler sample math.svg|right|280px|thumb|Mathematical text typeset using TeX and the [[AMS Euler]] font]]

Since the primary goal of the TeX language is high-quality typesetting for publishers of books, Knuth gave a lot of attention to the spacing rules for mathematical formulae.<ref>{{citation |title=Portraits in Silicon|first=Robert|last=Slater|publisher=MIT Press|date=1989|isbn=9780262691314 |page=349|url=https://books.google.com/books?id=aWTtMyYmKhUC&pg=PA349}}</ref><ref>{{citation|title=Digital Typography Using LaTeX|first1=Apostolos |last1=Syropoulos|first2=Antonis|last2=Tsolomitis|first3=Nick |last3=Sofroniou|publisher=Springer|date=2003|isbn=9780387952178 |url=https://books.google.com/books?id=LLYYisjrFdEC&pg=PA92|page=93}}</ref> He took three bodies of work that he considered to be standards of excellence for mathematical typography: the books typeset by the [[Addison-Wesley|Addison-Wesley Publishing]] house (the publisher of ''The Art of Computer Programming'') under the supervision of Hans Wolf; editions of the mathematical journal ''[[Acta Mathematica]]'' dating from around 1910; and a copy of ''[[Indagationes Mathematicae]]'', a [[Netherlands|Dutch]] mathematics journal. Knuth looked closely at these printed papers to sort out and look for a set of rules for spacing.<ref>{{Cite journal|last=Knuth |first=Donald E |title=Questions and Answers II |journal=TUGboat |volume=17 |date=1996 |pages=355–367}}</ref><ref name="DigitalTypography"/> While TeX provides some basic rules and the tools needed to specify proper spacing, the exact parameters depend on the font used to typeset the formula. For example, the spacing for Knuth's [[Computer Modern]] fonts has been precisely fine-tuned over the years and is now set; but when other fonts, such as [[AMS Euler]], were used by Knuth for the first time, new spacing parameters had to be defined.<ref>Knuth, Donald E. [http://www.tug.org/TUGboat/Articles/tb10-1/tb23knut.pdf ''Typesetting Concrete Mathematics''], TUGboat '''10''' (1989), pp. 31–36, 342. Reprinted as chapter 18 of ''Digital Typography'', pp. 367–378.</ref>

The typesetting of math in TeX is not without criticism, particularly with respect to technical details of the font metrics, which were designed in an era when significant attention was paid to storage requirements. This resulted in some "hacks" overloading some fields, which in turn required other "hacks". On an aesthetics level, the rendering of radicals has also been criticized.<ref>{{cite web |url=http://www.ntg.nl/maps/26/27.pdf |title=Math typesetting in TEX: The good, the bad, the ugly |last=Vieth |first=Ulrik |archive-url=https://web.archive.org/web/20220120120543/http://www.ntg.nl/maps/26/27.pdf |url-status=dead |archive-date=January 20, 2022}}</ref> The [[OpenType math]] font specification largely borrows from TeX, but has some new features/enhancements.<ref>{{cite web |url=http://blogs.msdn.com/b/murrays/archive/2006/09/13/752206.aspx|title=High-Quality Editing and Display of Mathematical Text in Office 2007}}</ref><ref>{{cite web |url=http://blogs.msdn.com/b/murrays/archive/2006/11/15/lineservices.aspx|title=LineServices}}</ref><ref>{{cite web|url=http://www.ntg.nl/maps/38/03.pdf |title=Map |website=ntg.nl}}</ref>

===Hyphenation and justification===
In comparison with manual typesetting, the problem of [[Justification (typesetting)|justification]] is easy to solve with a digital system such as TeX, which, provided that good points for line breaking have been defined, can automatically spread the spaces between words to fill in the line. The problem is thus to find the set of breakpoints that will give the most visually pleasing result. Many line-breaking algorithms use a [[greedy algorithm|''first-fit'' approach]], where the breakpoints for each line are determined one after the other, and no breakpoint is changed after it has been chosen.<ref>{{Citation | first = Michael P | last = Barnett | title = Computer Typesetting: Experiments and Prospects | place = [[Cambridge, Massachusetts|Cambridge]], [[Massachusetts|MA]] | publisher = [[MIT Press]] | date = 1965}}</ref> Such a system is not able to define a breakpoint depending on the effect that it will have on the following lines. In comparison, the ''total-fit'' line-breaking algorithm used by TeX and developed by Donald Knuth and Michael Plass <ref>url=http://svn.tug.org/interviews/plass.html</ref> considers ''all'' the possible breakpoints in a paragraph, and finds the combination of line breaks that will produce the most globally pleasing arrangement.

Formally, the algorithm defines a value called ''badness'' associated with each possible line break; the badness is increased if the spaces on the line must stretch or shrink too much to make the line the correct width. Penalties are added if a breakpoint is particularly undesirable: for example, if a word must be [[hyphen]]ated, if two lines in a row are hyphenated, or if a very loose line is immediately followed by a very tight line. The algorithm will then find the breakpoints that will minimize the sum of squares of the badness (including penalties) of the resulting lines. If the paragraph contains <math>n</math> possible breakpoints, the number of situations that must be evaluated naively is <math>2^n</math>. However, by using the method of [[dynamic programming]], the complexity of the algorithm can be brought down to <math>O(n^2)</math> (see [[Big O notation]]). Further simplifications (for example, not testing extremely unlikely breakpoints such as a hyphenation in the first word of a paragraph, or very overfull lines) lead to an efficient algorithm whose running time is <math>O(n w)</math>, where <math>w</math> is the width of a line. A similar algorithm is used to determine the best way to break paragraphs across two pages, in order to avoid [[Widow (typesetting)|widows]] or [[Orphan (typesetting)|orphans]] (lines that appear alone on a page while the rest of the paragraph is on the following or preceding page). However, in general, a thesis by Michael Plass shows how the page-breaking problem can be [[NP-complete]] because of the added complication of placing figures.{{Sfn | Knuth | Plass | 1981}} TeX's line-breaking algorithm has been adopted by several other programs, such as [[Adobe InDesign]] (a [[desktop publishing]] [[Computer application|application]])<ref>{{Citation | publisher = [[Advogato]] | url = http://www.advogato.org/article/28.html | type = interview | title = Donald E. Knuth| journal = TUGboat | volume = 21 | date = 2000 | pages = 103–10 | access-date = 26 December 2005 | archive-url = https://web.archive.org/web/20090122043044/http://www.advogato.org/article/28.html | archive-date = 22 January 2009 | url-status = dead }}</ref> and the [[GNU]] [[fmt (Unix)|fmt]] [[Unix]] [[command line]] utility.<ref>{{Citation|publisher=GNU Project |chapter-url=https://www.gnu.org/software/coreutils/manual/html_node/fmt-invocation.html#fmt-invocation |title=Core GNU utilities (GNU coreutils) manual |chapter=4.1 fmt: Reformat paragraph text |date=2016 }}</ref>

If no suitable line break can be found for a line, the system will try to hyphenate a word. The original version of TeX used a hyphenation algorithm based on a set of rules for the removal of prefixes and suffixes of words, and for deciding if it should insert a break between the two consonants in a pattern of the form [[vowel]]–[[consonant]]–[[consonant]]–[[vowel]] (which is possible most of the time).{{Sfn | Liang | 1983 | p = 3}} TeX82 introduced a new hyphenation algorithm, designed by [[Frank Liang]] in 1983, to assign priorities to breakpoints in letter groups. A list of hyphenation patterns is first generated automatically from a corpus of hyphenated words (a list of 50,000 words). If TeX must find the acceptable hyphenation positions in the word ''encyclopedia'', for example, it will consider all the subwords of the extended word ''.encyclopedia.'', where ''.'' is a special marker to indicate the beginning or end of the word. The list of subwords includes all the subwords of length 1 (''.'', ''e'', ''n'', ''c'', ''y'', etc.), of length 2 (''.e'', ''en'', ''nc'', etc.), etc., up to the subword of length 14, which is the word itself, including the markers. TeX will then look into its list of hyphenation patterns, and find subwords for which it has calculated the desirability of hyphenation at each position. In the case of our word, 11 such patterns can be matched, namely <sub>1</sub>c<sub>4</sub>l<sub>4</sub>, <sub>1</sub>cy, <sub>1</sub>d<sub>4</sub>i<sub>3</sub>a, <sub>4</sub>edi, e<sub>3</sub>dia, <sub>2</sub>i<sub>1</sub>a, ope<sub>5</sub>d, <sub>2</sub>p<sub>2</sub>ed, <sub>3</sub>pedi, pedia<sub>4</sub>, y<sub>1</sub>c. For each position in the word, TeX will calculate the ''maximum value'' obtained among all matching patterns, yielding en<sub>1</sub>cy<sub>1</sub>c<sub>4</sub>l<sub>4</sub>o<sub>3</sub>p<sub>4</sub>e<sub>5</sub>d<sub>4</sub>i<sub>3</sub>a<sub>4</sub>. Finally, the acceptable positions are those indicated by an [[even and odd numbers|odd]] number, yielding the acceptable hyphenations ''en-cy-clo-pe-di-a''. This system based on subwords allows the definition of very general patterns (such as <sub>2</sub>i<sub>1</sub>a), with low indicative numbers (either odd or even), which can then be superseded by more specific patterns (such as <sub>1</sub>d<sub>4</sub>i<sub>3</sub>a) if necessary. These patterns find about 90% of the hyphens in the original dictionary; more importantly, they do not insert any spurious hyphen. In addition, a list of exceptions (words for which the patterns do not predict the correct hyphenation) are included with the Plain TeX format; additional ones can be specified by the user.{{Sfn | Liang | 1983}}{{Rp | needed = yes | date = March 2013}}<ref>{{Citation | title = The TeXbook | chapter = Appendix H: Hyphenation | pages = 449–55}}</ref>

===Metafont===
{{main|Metafont}}

Metafont, not strictly part of TeX, is a font description system which allows the designer to describe characters algorithmically. It uses [[Bézier curve]]s in a fairly standard way to generate the actual characters to be displayed, but Knuth devotes substantial attention to the [[font rasterization|rasterizing]] problem on [[Raster graphics|bitmapped]] displays. Another thesis, by [[John Hobby]], further explores this problem of digitizing "brush trajectories". This term derives from the fact that Metafont describes characters as having been drawn by abstract brushes (and erasers). It is commonly believed that TeX is based on bitmap fonts but, in fact, these programs "know" nothing about the fonts that they are using other than their dimensions. It is the responsibility of the device driver to appropriately handle fonts of other types, including PostScript Type 1 and TrueType. Computer Modern (commonly known as "the TeX font") is freely available in Type 1 format, as are the AMS math fonts. Users of TeX systems that output directly to PDF, such as pdfTeX, XeTeX, or LuaTeX, generally never use Metafont output at all.

===Macro language===

TeX documents are written and programmed using an unusual macro language. Broadly speaking, the running of this macro language involves expansion and execution stages which do not interact directly. Expansion includes both literal expansion of macro definitions as well as conditional branching, and execution involves such tasks as setting variables/registers and the actual typesetting process of adding glyphs to boxes.

The definition of a macro not only includes a list of commands but also the syntax of the call. It differs with most widely used [[lexical preprocessor]]s like [[M4 (computer language)|M4]], in that the body of a macro gets tokenized at definition time.

The TeX macro language has been used to write larger document production systems, most notably including LaTeX and ConTeXt.

==Development==
The original source code for the current TeX software is written in [[WEB]], a mixture of documentation written in TeX and a [[Pascal programming language|Pascal]] subset in order to ensure  readability and portability. For example, TeX does all of its dynamic allocation itself from fixed-size arrays and uses only [[fixed-point arithmetic]] for its internal calculations. As a result, TeX has been ported to almost all [[operating system]]s, usually by using the [[web2c]] program to convert the source code into [[C (programming language)|C]] instead of directly compiling the Pascal code. Knuth has kept a very detailed log of all the bugs he has corrected and changes he has made in the program since 1982; {{As of|2021|lc=on}}, the list contains 440 entries, not including the version modification that should be done after his death as the final change in TeX.<ref>Knuth, Donald E. [https://ctan.org/tex-archive/systems/knuth/dist/errata/tex82.bug List of updates to the TeX82 listing published in September 1982], available on [[CTAN]].</ref><ref>Knuth, Donald E. [ftp://tug.ctan.org/pub/tex-archive/systems/knuth/dist/errata/errorlog.tex Appendix to the ''Errors of TeX'' paper], available on CTAN, last modified in January 2003.</ref> Knuth offers [[Knuth reward check|monetary awards]] to people who find and report a [[Computer bug|bug]] in TeX. The award per bug started at US$2.56 (one "hexadecimal dollar"<ref>{{cite web |url=http://www-cs-faculty.stanford.edu/~knuth/faq.html |title=Knuth: Frequently Asked Questions |first=Donald E |last=Knuth |access-date=2019-11-28 |website=Stanford Computer Science |archive-url=https://web.archive.org/web/20080306101505/http://www-cs-faculty.stanford.edu/~knuth/faq.html |archive-date=6 March 2008 |url-status=dead }}</ref>) and doubled every year until it was frozen at its current value of $327.68. Knuth has lost relatively little money as there have been very few bugs claimed. In addition, recipients have been known to frame their check as proof that they found a bug in TeX rather than cashing it.<ref>{{cite web |url=http://www.stanfordalumni.org/news/magazine/2006/mayjun/features/knuth.html |title=Love at First Byte |author=Kara Platoni |website=[[Stanford Magazine]] |date=May–June 2006 |url-status=dead |archive-url=https://web.archive.org/web/20060604115901/http://www.stanfordalumni.org/news/magazine/2006/mayjun/features/knuth.html |archive-date=2006-06-04 }}</ref><ref>{{cite web |url=http://www.tug.org/whatis.html |title=History of TeX |website=TeX Users Group |access-date=2019-11-28}}</ref>

Due to scammers finding scanned copies of his checks on the internet and using them to try to drain his bank account, Knuth no longer sends out real checks, but those who submit bug reports can get credit at [[San Serriffe#National Bank|The Bank of San Serriffe]] instead.<ref>{{cite web |url=http://www-cs-faculty.stanford.edu/~knuth/news08.html |title=Knuth: Recent News – Financial Fiasco |first=Donald E |last=Knuth |date=2008 |website=Stanford Computer Science |access-date=29 November 2019 |archive-date=29 November 2019 |archive-url=https://web.archive.org/web/20191129030740/https://www-cs-faculty.stanford.edu/~knuth/news08.html |url-status=dead }}</ref>

==Distributions and extensions==
TeX is usually provided in the form of an easy-to-install bundle of TeX itself along with [[Metafont]] and all the necessary fonts, documents formats, and utilities needed to use the typesetting system. On UNIX-compatible systems, including [[Linux]] and [[Apple, Inc.|Apple]] [[macOS]], TeX is distributed as part of the larger [[TeX Live]] distribution. (Prior to TeX Live, the [[teTeX]] distribution was the de facto standard on UNIX-compatible systems.) On [[Microsoft Windows]], there is the [[MiKTeX]] distribution (enhanced by proTeXt) and the Microsoft Windows version of TeX Live.

Several document processing systems are based on TeX, notably [[jadeTeX]], which uses TeX as a backend for printing from [[James Clark (XML expert)|James Clark]]'s [[Document Style Semantics and Specification Language|DSSSL Engine]], the [[Arbortext]] publishing system, and [[Texinfo]], the GNU documentation processing system. TeX has been the official typesetting package for the GNU operating system since 1984.

Numerous extensions and companion programs for TeX exist, among them [[BibTeX]] for bibliographies (distributed with LaTeX); pdfTeX, a TeX-compatible engine which can directly produce PDF output (as well as continuing to support the original DVI output); [[XeTeX]], a TeX-compatible engine that supports [[Unicode]] and [[OpenType]]; and [[LuaTeX]], a Unicode-aware extension to TeX that includes a Lua runtime with extensive hooks into the underlying TeX routines and algorithms. Most TeX extensions are available for free from [[CTAN]], the Comprehensive TeX Archive Network.

===Editors===
{{See also|Comparison of TeX editors}}

There are a variety of [[:Category:TeX editors|editors designed to work with TeX]]:

# The [[GNU TeXmacs|TeXmacs]] text editor is a [[WYSIWYG]]-[[WYSIWYM]] scientific text editor, inspired by both TeX and [[Emacs]]. It uses Knuth's fonts and can generate TeX output.
#[[Overleaf]] is a partial-WYSIWYG, online editor that provides a cloud-based solution to TeX along with additional features in real-time collaborative editing.
# [[LyX]] is a [[WYSIWYM]] document processor which runs on a variety of platforms including: 
## [[Linux]], 
## [[Microsoft Windows]] (newer versions require Windows 2000 or later) 
## Apple [[macOS]] (using a non-native [[Qt (toolkit)|Qt]] front-end). 
# [[TeXShop]] (for macOS), [[TeXworks]] (for Linux, macOS and Windows) and [[WinShell]] (for Windows) are similar tools and provide an integrated development environment (IDE) for working with LaTeX or TeX. For [[KDE]]/Qt, [[Kile]] provides such an IDE. 
# [[Texmaker]] is the Pure Qt equivalent of Kile, with a user interface that is nearly the same as Kile's.
# [[TeXstudio]] is an open-source fork (2009) of [[Texmaker]] that offers a different approach to configurability and features. Free downloadable binaries are provided for Windows, Linux, macOS, OS/2, and FreeBSD.
# [[GNU Emacs]] has various built-in and third-party packages with support for TeX, the major one being [[AUCTeX]]. 
# [[Visual Studio Code]].  A notable extension is LaTeX Workshop
# For [[Vim (text editor)|Vim]], possible plugins include Vim-LaTeX Suite,<ref>{{Citation | title = Vim-LaTex | publisher = SourceForge | url = http://vim-latex.sourceforge.net/ |url-status=live |archive-url=https://web.archive.org/web/20240308132826/https://vim-latex.sourceforge.net/ |archive-date= Mar 8, 2024 }}</ref> Automatic TeX,<ref>{{Citation | title = Automatic TeX plugin | url = https://launchpad.net/automatictexplugin | publisher = Launch pad }} {{Dead link|date=June 2018 |bot=InternetArchiveBot |fix-attempted=no }}</ref> and TeX-9.<ref>{{Citation | title = TeX-9 | url = http://www.vim.org/scripts/script.php?script_id=3508 | publisher = Vim.org}}</ref> 
# For [[Apache OpenOffice]] and [[LibreOffice]], iMath and TexMaths extensions can provide mathematical TeX typesetting.<ref>{{Citation | title = TexMaths Homepage | publisher = free.fr | url = http://roland65.free.fr/texmaths/}}</ref><ref>{{Citation | title = iMath | publisher = SourceForge | url = https://ooo-imath.sourceforge.io/wiki/index.php/Main_Page}}</ref>
# For [[MediaWiki]], the [[mw:Extension:Math|Math extension]] provides mathematical TeX typesetting, but the code needs to be surrounded by <code><math></code> tag.

===Licence===
Donald Knuth has indicated several times<ref>{{cite journal |last1=Knuth |first1=Donald E. |date=1986 |title=Remarks to Celebrate the Publication of Computers & Typesetting |url=https://tug.org/TUGboat/tb07-2/tb15knut.pdf |journal=TUGboat |volume=7 |issue=2 |pages=95–98 |access-date=6 December 2024}}</ref><ref>{{cite journal |last1=Knuth |first1=Donald E. |date=1990 |title=The Future of TeX and METAFONT |url=https://www.tug.org/TUGboat/tb11-4/tb30knut.pdf |journal=TUGboat |volume=11 |issue=4 |page=489 |access-date=6 December 2024}}</ref><ref>{{cite web |url=https://www.kyotoprize.org/wp-content/uploads/2019/07/1996_A.pdf |title=Digital Typography: 1996 Kyoto Prize Lecture |last=Knuth |first=Donald Ervin |publisher=The Inamori Foundation |date=November 1, 1997 |website=Kyoto Prize |access-date=December 6, 2024}}</ref><ref name="DigitalTypography">{{cite book | last=Knuth | first=Donald E. | title=Digital Typography | publisher=Center for the Study of Language and Information Publications | publication-place=Stanford, Calif | date=1999 | isbn=978-1-57586-010-7 }}</ref> that the source code of TeX has been placed into the "[[public domain]]", and he strongly encourages modifications or experimentations with this source code. However, since Knuth highly values the reproducibility of the output of all versions of TeX, any changed version must not be called TeX, or anything confusingly similar. To enforce this rule, any implementation of the system must pass a test suite called the TRIP test<ref>{{Citation |url=ftp://tug.ctan.org/pub/tex-archive/systems/knuth/dist/tex/trip.tex |title=CTAN |contribution=Trip |type=source code |format=TeX}}</ref> before being allowed to be called TeX. The question of licence is somewhat confused by the statements included at the beginning of the TeX source code,<ref>{{Citation |first=Donald E |last=Knuth |title=TeX: The Program |series=Computers and Typesetting |volume=B |place=Reading, MA |publisher=Addison-Wesley |year=1986 |isbn=0-201-13437-3 |url-access=registration |url=https://archive.org/details/texprogram00knut}}</ref> which indicate that "all rights are reserved. Copying of this file is authorized only if&nbsp;... you make absolutely no changes to your copy". This restriction should be interpreted as a prohibition to change the source code ''as long as the file is called tex.web''. The copyright note at the beginning of tex.web (and mf.web) was changed in 2021 to explicitly state this. This interpretation is confirmed later in the source code when the TRIP test is mentioned ("If this program is changed, the resulting system should not be called 'TeX{{'"}}).<ref>[https://books.google.com/books?id=PA-Rhb_QSAwC&dq=tex+in+public+domain+knuth&pg=PA227 Open Source: Technology and Policy] by Fadi P. Deek, James A. M. McHugh "Public domain", page 227 (2008)</ref> The [[American Mathematical Society]] tried in the early 1980s to claim a [[trademark]] for TeX. This was rejected because at the time "TEX" (all caps) was registered by [[Honeywell]] for the "[[Text Executive Programming Language|Text EXecutive]]" text processing system.{{Citation needed|date=April 2010}}

=== XML publication ===
It is possible to use TeX for automatic generation of sophisticated layout for XML data. The differences in syntax between the two description languages can be overcome with the help of [[TeXML]]. In the context of XML publication, TeX can thus be considered an alternative to [[XSL Formatting Objects|XSL-FO]]. TeX allowed scientific papers in mathematical disciplines to be reduced to relatively small files that could be rendered client-side, allowing fully typeset scientific papers to be exchanged over the early Internet and emerging World Wide Web, even when sending large files was difficult. This paved the way for the creation of repositories of scientific papers such as [[arXiv]], through which papers could be 'published' without an intermediary publisher.<ref>{{cite journal|last1=O'Connell|first1=Heath|title=Physicists Thriving with Paperless Publishing |journal=Hep Lib.web.|year=2002 |volume=6|page=3|arxiv=physics/0007040 }}</ref>

==Pronunciation and spelling==
The name TeX is intended by its developer to be pronounced {{IPAc-en|t|ɛ|x}}, with the final consonant of ''loch.''<ref>Knuth, Donald E. ''The TeXbook'', Ch.&nbsp;1: The Name of the Game, p.&nbsp;1.</ref> The letters of the name are meant to represent the [[capital letter|capital]] [[Greek alphabet|Greek]] letters [[tau]], [[epsilon]], and [[chi (letter)|chi]], as TeX is an abbreviation of [[techne|τέχνη]] ({{lang|grc|ΤΕΧΝΗ}} {{transl|grc|technē}}), Greek for both "art" and "craft", which is also the root word of ''technical''. English speakers often pronounce it {{IPAc-en|t|ɛ|k}}, like the first syllable of ''technical''. Knuth instructs that it be typeset with the "E" below the baseline and reduced spacing between the letters. This is done, as Knuth mentions in his ''TeXbook'', to distinguish TeX from other system names such as [[Text Executive Programming Language|TEX, the Text EXecutive processor]] (developed by Honeywell Information Systems).<ref>Knuth, Donald E. [http://www.tug.org/TUGboat/Articles/tb07-2/tb15knutlogo.pdf ''The TeX Logo in Various Fonts''], [[TUGboat]] '''7''' (1986), 101. Reprinted as chapter 6 of ''Digital Typography''.</ref> Fans like to proliferate names from the word "TeX"—such as ''TeXnician'' (user of TeX software), ''TeXhacker'' (TeX programmer), ''TeXmaster'' (competent TeX programmer), ''TeXhax'', and ''TeXnique''.<ref>{{cite web | url=http://www.catb.org/jargon/html/T/TeX.html | title=The Jargon File—TeX | access-date=23 July 2016}}</ref>

==Community==
[[File:Logo TUG.svg|thumb|upright=0.4|TeX Users Group's logo]]

Notable entities in the TeX community include the TeX Users Group (TUG), which currently publishes ''[[TUGboat]]'' and formerly published ''[[The PracTeX Journal]]'', covering a wide range of topics in [[digital typography]] relevant to TeX. The [[Deutschsprachige Anwendervereinigung TeX]] (DANTE) is a large user group in Germany. The TeX Users Group was founded in 1980 for educational and scientific purposes, provides an organization for those who have an interest in typography and font design, and are users of the TeX typesetting system invented by Knuth. The TeX Users Group represents the interests of TeX users worldwide. The TeX Users Group publishes the [[scientific journal|journal]] ''[[TUGboat]]'' three times per year;<ref>{{cite web |title=The Communications of the TeX Users Group |url=http://www.tug.org/TUGboat/ |website=tug.org |publisher=TeX Users Group |access-date=15 March 2019}}</ref> DANTE publishes ''{{ill|Die TeXnische Komödie|de}}'' four times per year. Other user groups include DK-TUG in [[Denmark]], {{ill|GUTenberg|fr}} in [[France]], GuIT in [[Italy]], NTG in the Netherlands and UK-TUG in the [[United Kingdom]]; the user groups jointly maintain a complete list.<ref>{{cite web|title=All TeX User Groups|url=https://tug.org/usergroups.html|website=tug.org|publisher=TeX Users Group|access-date=17 November 2019}}</ref>

== Extensions ==

* [[List of TeX extensions]]

==See also==
{{div col|colwidth=22em}}
* [[Comparison of document markup languages]]
* [[Formula editor]]
* [[List of document markup languages]]
* [[MathJax]] - TeX on Web pages via JavaScript
* [[MathTime]]
* [[New Typesetting System]] – a TeX reimplementation (discontinued)
* [[PGF/TikZ]]
* [[PSTricks]]
* [[xdvi]] – a program for viewing .dvi files
* [[Help:Displaying a formula]], for help displaying mathematical formulae in Wikipedia

{{div col end}}
{{Portal bar|Free and open-source software|Mathematics}}

==Notes==
{{notelist}}
{{reflist|group=Note}}

==References==
{{reflist}}

===Sources===
{{Refbegin|30em}}
* {{Citation | first = Nelson HF | last = Beebe | url = http://www.tug.org/TUGboat/Articles/tb25-1/beebe-2003keynote.pdf | title = 25 Years of TeX and METAFONT: Looking Back and Looking Forward | journal = TUGboat | volume = 25 | date = 2004 | pages = 7–30}}.
* {{Citation | first = Donald Ervin | last = Knuth | title = The TeXbook | series = [[Computers and Typesetting]] | volume = A | place = Reading, [[Massachusetts|MA]] | publisher = Addison-Wesley | date = 1984 | isbn = 0-201-13448-9 | url-access = registration | url = https://archive.org/details/texbook00dona }}.  The [http://www.ctan.org/tex-archive/systems/knuth/dist/tex/texbook.tex source code of the book in TeX] (and a needed set of macros [ftp://tug.ctan.org/pub/tex-archive/systems/knuth/dist/lib/manmac.tex]) is available online on [[CTAN]]. It is provided only as an example and its use to prepare a book like The TeXbook is not allowed.
* {{Citation | first = Donald Ervin | last = Knuth | author-mask = 3 | title = TeX: The Program | series = Computers and Typesetting | volume = B | place = Reading, [[Massachusetts|MA]] | publisher = Addison-Wesley | date = 1986 | isbn = 0-201-13437-3 | url-access = registration | url = https://archive.org/details/texprogram00knut }}. The full source code of TeX; also [ftp://tug.ctan.org/pub/tex-archive/systems/knuth/dist/tex/tex.web available] on [[CTAN]]. Being written using [[literate programming]], it contains plenty of human-readable documentation.
* {{Citation | first = Donald Ervin | last = Knuth | author-mask = 3 | title = Digital Typography | series = Lecture notes | number = 78 | publisher = Center for the Study of Language and Information | date = 1999 | isbn = 1-57586-010-4 | url-access = registration | url = https://archive.org/details/digitaltypograph0000knut }}.
* {{Cite journal | first1 = Donald Ervin | last1 = Knuth | author-mask = 3 | first2 = Michael F | last2 = Plass | title = Breaking Paragraphs into Lines | journal = Software: Practice and Experience | volume = 11 | date = 1981 | issue = 11 | pages = 1119–84 | doi=10.1002/spe.4380111102| s2cid = 206508107 }}.
* {{Citation | first = Donald Ervin | last = Knuth | author-mask = 3 | url = http://www.tex.ac.uk/ctan/systems/knuth/dist/tex/ | title = TeX | type = source code | format = [[WEB]] | url-status = dead | archive-url = https://web.archive.org/web/20110927042518/http://www.tex.ac.uk/ctan/systems/knuth/dist/tex/ | archive-date = 27 September 2011}} contains extensive documentation about the algorithms used in TeX.
* {{Citation | first = Leslie | last = Lamport | author-link = Leslie Lamport | title = [[LaTeX]]: A Document Preparation System | place = Reading, [[Massachusetts|MA]] | publisher = Addison-Wesley | edition = 2nd | date = 1994 | isbn = 0-201-52983-1}}.
* {{Citation | first = Franklin Mark | last = Liang | url = http://www.tug.org/docs/liang/ | title = Word Hy-phen-a-tion by Com-put-er | type = [[PhD]] thesis | publisher = Department of Computer Science, [[Stanford University]] |date=August 1983}}.
* {{Citation | first = David | last = Salomon | title = The Advanced TeXbook | publisher = Springer | date = 1995 | bibcode = 1995adte.book.....S | isbn = 0-387-94556-3}}.
* {{Citation | first = MD | last = Spivak | title = The Joy of TeX | edition = 2nd | publisher = American Mathematical Society | date = 1990 | isbn = 0-8218-2997-1 | type = reference}} on AMS-TeX.
* {{Citation | first = Michael | last = Vulis | url = https://books.google.com/books?id=UfUdto-Sz9QC | title = Modern TeX and Its Applications | publisher = CRC Press | date = 1992 | isbn = 0-8493-4431-X}}.
{{Refend}}

==External links==
{{Sisterlinks|b=TeX|commons=TeX|d=Q5301|voy=no|s=no|species=no|n=no|m=no|mw=no|q=no}}
*[http://www.tug.org/ TeX Users' Group]
* {{Citation | url = https://tex.stackexchange.com/ | title = TeX | type = questions and answers | publisher = StackExchange}}.
* Eijkhout, Victor. [http://www.eijkhout.net/tbt/ ''TeX by Topic''] {{Webarchive|url=https://web.archive.org/web/20210225003039/http://www.eijkhout.net/tbt/ |date=25 February 2021 }}
* [http://ftp.gwdg.de/pub/ctan/info/impatient/book.pdf ''TeX for the Impatient'']
*Donald Knuth discusses developing the software for TEX at Xerox PARC 2/21/1980  https://archive.org/details/xerox-parc-tapes-v49

{{TeX navbox|state=expanded}}
{{TeX editors}}
{{Free and open-source typography}}
{{Donald Knuth navbox}}
{{Authority control}}

{{DEFAULTSORT:Tex}}
[[Category:TeX| ]]
[[Category:1978 software]]
[[Category:Desktop publishing software]]
[[Category:Digital typography]]
[[Category:Donald Knuth]]
[[Category:Free TeX software]]
[[Category:Macro programming languages]]
[[Category:Typesetting software]]
[[Category:Typesetting]]
[[Category:Markup languages]]