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102-438: TeX ( / t ɛ x / , see below ), stylized within the system as T e X , is a typesetting program which was designed and written by computer scientist and Stanford University professor Donald Knuth and first released in 1978. The term now refers to the system of extensions – which includes software programs called TeX engines , sets of TeX macros , and packages which provide extra typesetting functionality – built around

204-438: A 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. The base TeX system understands about 300 commands, called primitives . These low-level commands are rarely used directly by users, and most functionality

306-474: A 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 systems , usually by using the web2c program to convert the source code into C instead of directly compiling the Pascal code. Knuth has kept

408-641: A trademark for TeX. This was rejected because at the time "TEX" (all caps) was registered by Honeywell for the " Text EXecutive " text processing system. 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-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

510-403: A Compugraphics system for typesetting and page layout. The magazine did not yet accept articles on floppy disks, but hoped to do so "as matters progress". Before the 1980s, practically all typesetting for publishers and advertisers was performed by specialist typesetting companies. These companies performed keyboarding, editing and production of paper or film output, and formed a large component of

612-535: 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. There are

714-418: A copy of Indagationes Mathematicae , a Dutch mathematics journal. Knuth looked closely at these printed papers to sort out and look for a set of rules for spacing. 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

816-575: A custom LaTeX-inspired markup (SIL) or in XML. Via the adjunction of 3rd-party modules, composition in Markdown or Djot is also possible. Hyphenation algorithm Syllabification ( / s ɪ ˌ l æ b ɪ f ɪ ˈ k eɪ ʃ ən / ) or syllabication ( / s ɪ ˌ l æ b ɪ ˈ k eɪ ʃ ən / ), also known as hyphenation , is the separation of a word into syllables , whether spoken, written or signed. The written separation into syllables

918-455: A different text syntax specifically for mathematical formulas. For example, the quadratic formula (which is the solution of the quadratic equation ) appears as: 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

1020-421: A fairly standard way to generate the actual characters to be displayed, but Knuth devotes substantial attention to the rasterizing problem on 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

1122-401: A family of typesetting languages with names that were derivatives of the word "SCRIPT". Later versions of SCRIPT included advanced features, such as automatic generation of a table of contents and index, multicolumn page layout, footnotes, boxes, automatic hyphenation and spelling verification. NSCRIPT was a port of SCRIPT to OS and TSO from CP-67/CMS SCRIPT. Waterloo Script was created at

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1224-405: 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 tex myfile.tex 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

1326-479: A frame, making up a form or page. If done correctly, all letters were of the same height, and a flat surface of type was created. The form was placed in a press and inked, and then printed (an impression made) on paper. Metal type read backwards, from right to left, and a key skill of the compositor was their ability to read this backwards text. Before computers were invented, and thus becoming computerized (or digital) typesetting, font sizes were changed by replacing

1428-431: A hyphenation in the first word of a paragraph, or very overfull lines) lead to an efficient algorithm whose running time is O ( n w ) {\displaystyle O(nw)} , where w {\displaystyle w} 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 widows or orphans (lines that appear alone on

1530-479: A keyboard or other devices could produce the desired text. Most of the successful systems involved the in-house casting of the type to be used, hence are termed "hot metal" typesetting. The Linotype machine , invented in 1884, used a keyboard to assemble the casting matrices, and cast an entire line of type at a time (hence its name). In the Monotype System , a keyboard was used to punch a paper tape , which

1632-408: A light source to selectively expose characters onto light-sensitive paper. Originally they were driven by pre-punched paper tapes . Later they were connected to computer front ends. One of the earliest electronic photocomposition systems was introduced by Fairchild Semiconductor . The typesetter typed a line of text on a Fairchild keyboard that had no display. To verify correct content of the line it

1734-521: 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). 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

1836-486: A lot of attention to the spacing rules for mathematical formulae. He took three bodies of work that he considered to be standards of excellence for mathematical typography: the books typeset by the 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

1938-518: 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. TeX's line-breaking algorithm has been adopted by several other programs, such as Adobe InDesign (a desktop publishing application ) and the GNU fmt Unix command line utility. If no suitable line break can be found for

2040-710: A result, even most native English speakers are unable to syllabify words according to established rules without consulting a dictionary or using a word processor. Schools usually do not provide much more advice on the topic than to consult a dictionary. In addition, there are differences between British and US syllabification and even between dictionaries of the same English variety. In Finnish , Italian , Portuguese , Japanese ( Romaji ), Korean ( Romanized ) and other nearly phonemically spelled languages, writers can in principle correctly syllabify any existing or newly created word using only general rules. In Finland, children are first taught to hyphenate every word until they produce

2142-483: 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,

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2244-465: A system associated with technical typesetting. TeX commands commonly start with a backslash and are grouped with 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 - and 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

2346-511: A type case with the right hand, and set from left to right into a composing stick held in the left hand, appearing to the typesetter as upside down. As seen in the photo of the composing stick, a lower case 'q' looks like a 'd', a lower case 'b' looks like a 'p', a lower case 'p' looks like a 'b' and a lower case 'd' looks like a 'q'. This is reputed to be the origin of the expression "mind your p's and q's". It might just as easily have been "mind your b's and d's". A forgotten but important part of

2448-708: A user to mix texts written in left-to-right and right-to-left writing systems in the same document. 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 . Numerous journals in these fields are produced using TeX or LaTeX, allowing authors to submit their raw manuscript written in TeX. While many publications in other fields, including dictionaries and legal publications, have been produced using TeX, it has not been as successful as in

2550-462: A variety of editors designed to work with TeX : Donald Knuth has indicated several times 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

2652-422: A very detailed log of all the bugs he has corrected and changes he has made in the program since 1982; as of 2021, the list contains 440 entries, not including the version modification that should be done after his death as the final change in TeX. Knuth offers monetary awards to people who find and report a bug in TeX. The award per bug started at US$ 2.56 (one "hexadecimal dollar") and doubled every year until it

2754-705: 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. TeX documents are written and programmed using an unusual macro language. Broadly speaking,

2856-624: Is considered fairly difficult to learn on its own, and deals more with appearance than structure. The LaTeX macro package, written by Leslie Lamport at the beginning of the 1980s, offered a simpler interface and an easier way to systematically encode the structure of a document. LaTeX markup is widely used in academic circles for published papers and books. Although standard TeX does not provide an interface of any sort, there are programs that do. These programs include Scientific Workplace and LyX , which are graphical/interactive editors; TeXmacs , while being an independent typesetting system, can also aid

2958-480: Is done, as Knuth mentions in his TeXbook , to distinguish TeX from other system names such as TEX, the Text EXecutive processor (developed by Honeywell Information Systems). 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 . Notable entities in the TeX community include

3060-478: 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

3162-466: Is now very stable, and only minor updates are anticipated. The current version of TeX is 3.141592653; it was last updated in 2021. 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 bug fixes. 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

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3264-488: 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-complete language even at the expansion level. 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

3366-701: 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., amsmath , amssymb ) and the "AMS document classes" (e.g., amsart , amsbook ). This is then referred to as AMS-LaTeX . Other formats include ConTeXt , used primarily for desktop publishing and written mostly by Hans Hagen at Pragma . A sample Hello world program in plain TeX is: This might be in

3468-460: 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. 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 ,

3570-574: Is still included with a number of Unix and Unix-like systems, and has been used to typeset a number of high-profile technical and computer books. Some versions, as well as a GNU work-alike called groff , are now open source . The TeX system, developed by Donald E. Knuth at the end of the 1970s, is another widespread and powerful automated typesetting system that has set high standards, especially for typesetting mathematics. LuaTeX and LuaLaTeX are variants of TeX and of LaTeX scriptable in Lua . TeX

3672-786: 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 's 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,

3774-407: 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. Since version 3, TeX has used an idiosyncratic 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 π . This is a reflection of the fact that TeX

3876-528: Is usually marked by a hyphen when using English orthography (e.g., syl-la-ble) and with a period when transcribing the actually spoken syllables in the International Phonetic Alphabet (e.g., [ˈsɪl.ə.bᵊɫ] ). For presentation purposes, typographers may use an interpunct ( Unicode character U+00B7, e.g., syl·la·ble), a special-purpose "hyphenation point" (U+2027, e.g., syl‧la‧ble), or a space (e.g., syl la ble). At

3978-459: 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 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

4080-657: The Apple Macintosh , Aldus PageMaker (and later QuarkXPress ) and PostScript and on the PC platform with Xerox Ventura Publisher under DOS as well as Pagemaker under Windows. Improvements in software and hardware, and rapidly lowering costs, popularized desktop publishing and enabled very fine control of typeset results much less expensively than the minicomputer dedicated systems. At the same time, word processing systems, such as Wang , WordPerfect and Microsoft Word , revolutionized office documents. They did not, however, have

4182-560: The Metafont language for font description and the Computer Modern family of typefaces ). TeX is free software , which made it accessible to a wide range of users. When the first paper volume of Knuth's The Art of Computer Programming was published in 1968, it was typeset using hot metal typesetting on a Monotype machine . This method, dating back to the 19th century, produced a "classic style" appreciated by Knuth. When

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4284-560: The United Kingdom ; the user groups jointly maintain a complete list. Typesetting During much of the letterpress era , movable type was composed by hand for each page by workers called compositors . A tray with many dividers, called a case, contained cast metal sorts , each with a single letter or symbol, but backwards (so they would print correctly). The compositor assembled these sorts into words, then lines, then pages of text, which were then bound tightly together by

4386-550: The algorithmic approaches to hyphenation, the one implemented in the TeX typesetting system is widely used. It is thoroughly documented in the first two volumes of Computers and Typesetting by Donald Knuth and in Franklin Mark Liang's dissertation. The aim of Liang's work was to get the algorithm as accurate as possible and to keep exceptions to a minimum. In TeX's original hyphenation patterns for American English,

4488-405: The capital Greek letters tau , epsilon , and chi , as TeX is an abbreviation of τέχνη ( ΤΕΧΝΗ technē ), Greek for both "art" and "craft", which is also the root word of technical . English speakers often pronounce it / 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

4590-399: The total-fit line-breaking algorithm used by TeX and developed by Donald Knuth and Michael Plass 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

4692-591: The 1970s and early 1980s, such as Datalogics Pager, Penta, Atex , Miles 33, Xyvision, troff from Bell Labs , and IBM's Script product with CRT terminals, were better able to drive these electromechanical devices, and used text markup languages to describe type and other page formatting information. The descendants of these text markup languages include SGML , XML and HTML . The minicomputer systems output columns of text on film for paste-up and eventually produced entire pages and signatures of 4, 8, 16 or more pages using imposition software on devices such as

4794-542: The 1980s by fully digital systems employing a raster image processor to render an entire page to a single high-resolution digital image , now known as imagesetting. The first commercially successful laser imagesetter, able to make use of a raster image processor, was the Monotype Lasercomp. ECRM, Compugraphic (later purchased by Agfa ) and others rapidly followed suit with machines of their own. Early minicomputer -based typesetting software introduced in

4896-601: The Israeli-made Scitex Dolev. The data stream used by these systems to drive page layout on printers and imagesetters, often proprietary or specific to a manufacturer or device, drove development of generalized printer control languages, such as Adobe Systems ' PostScript and Hewlett-Packard 's PCL . Computerized typesetting was so rare that BYTE magazine (comparing itself to "the proverbial shoemaker's children who went barefoot") did not use any computers in production until its August 1979 issue used

4998-579: 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

5100-642: The TeX typesetting system invented by Knuth. The TeX Users Group represents the interests of TeX users worldwide. The TeX Users Group publishes the journal TUGboat three times per year; DANTE publishes Die TeXnische Komödie  [ de ] four times per year. Other user groups include DK-TUG in Denmark , GUTenberg  [ fr ] in France , GuIT in Italy , NTG in the Netherlands and UK-TUG in

5202-582: The University of Waterloo (UW) later. One version of SCRIPT was created at MIT and the AA/CS at UW took over project development in 1974. The program was first used at UW in 1975. In the 1970s, SCRIPT was the only practical way to word process and format documents using a computer. By the late 1980s, the SCRIPT system had been extended to incorporate various upgrades. The initial implementation of SCRIPT at UW

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5304-426: The bed of a press. In this process, called stereotyping , the entire form is pressed into a fine matrix such as plaster of Paris or papier mâché to create a flong , from which a positive form is cast in type metal . Advances such as the typewriter and computer would push the state of the art even farther ahead. Still, hand composition and letterpress printing have not fallen completely out of use, and since

5406-429: 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

5508-457: The characters with a different size of type. In letterpress printing, individual letters and punctuation marks were cast on small metal blocks, known as "sorts," and then arranged to form the text for a page. The size of the type was determined by the size of the character on the face of the sort. A compositor would need to physically swap out the sorts for a different size to change the font size. During typesetting, individual sorts are picked from

5610-597: 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 . 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 , to ensure reproducibility of

5712-484: The concern of the casterman, is the "set", or width of each sort. Set width, like body size, is measured in points. In order to extend the working life of type, and to account for the finite sorts in a case of type, copies of forms were cast when anticipating subsequent printings of a text, freeing the costly type for other work. This was particularly prevalent in book and newspaper work where rotary presses required type forms to wrap an impression cylinder rather than set in

5814-490: The conversion to do-it-yourself easier, but also opened up a gap between skilled designers and amateurs. The advent of PostScript, supplemented by the PDF file format, provided a universal method of proofing designs and layouts, readable on major computers and operating systems. QuarkXPress had enjoyed a market share of 95% in the 1990s, but lost its dominance to Adobe InDesign from the mid-2000s onward. IBM created and inspired

5916-422: The correct syllabification reliably, after which the hyphens can be omitted. A hyphenation algorithm is a set of rules, especially one codified for implementation in a computer program, that decides at which points a word can be broken over two lines with a hyphen. For example, a hyphenation algorithm might decide that impeachment can be broken as impeach-ment or im-peachment but not impe-achment . One of

6018-422: 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. The name TeX is intended by its developer to be pronounced / t ɛ x / , with the final consonant of loch. The letters of the name are meant to represent

6120-452: The end of a line, a word is separated in writing into parts, conventionally called "syllables", if it does not fit the line and if moving it to the next line would make the first line much shorter than the others. This can be a particular problem with very long words, and with narrow columns in newspapers. Word processing has automated the process of justification , making syllabification of shorter words often unnecessary. In some languages,

6222-458: The exception list contains only 14 words. Ports of the TeX hyphenation algorithm are available as libraries for several programming languages, including Haskell , JavaScript , Perl , PostScript , Python , Ruby , C# , and TeX can be made to show hyphens in the log by the command \showhyphens . In LaTeX , hyphenation correction can be added by users by using: The \hyphenation command declares allowed hyphenation points in which words

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6324-566: The graphic arts industry. In the United States, these companies were located in rural Pennsylvania, New England or the Midwest, where labor was cheap and paper was produced nearby, but still within a few hours' travel time of the major publishing centers. In 1985, with the new concept of WYSIWYG (for What You See Is What You Get) in text editing and word processing on personal computers, desktop publishing became available, starting with

6426-466: The help of scripting languages. YesLogic's Prince is another one, which is based on CSS Paged Media. During the mid-1970s, Joe Ossanna , working at Bell Laboratories , wrote the troff typesetting program to drive a Wang C/A/T phototypesetter owned by the Labs; it was later enhanced by Brian Kernighan to support output to different equipment, such as laser printers . While its use has fallen off, it

6528-504: 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. Metafont, not strictly part of TeX, is a font description system which allows the designer to describe characters algorithmically. It uses Bézier curves in

6630-508: The introduction of digital typesetting, it has seen a revival as an artisanal pursuit. However, it is a small niche within the larger typesetting market. The time and effort required to manually compose the text led to several efforts in the 19th century to produce mechanical typesetting. While some, such as the Paige compositor , met with limited success, by the end of the 19th century, several methods had been devised whereby an operator working

6732-417: 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 hyphenated , 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

6834-427: 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 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. Such a system is not able to define a breakpoint depending on the effect that it will have on the following lines. In comparison,

6936-434: The living language. Seeing only lear- at the end of a line might mislead the reader into pronouncing the word incorrectly, as the digraph ea can hold many different values . The history of English orthography accounts for such phenomena. English written syllabification therefore deals with a concept of "syllable" that does not correspond to the linguistic concept of a phonological (as opposed to morphological) unit. As

7038-547: 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), most people have extended TeX only using macros and it has remained

7140-418: The negative film, resulting in a column of black type on white paper, or a galley . The galley was then cut up and used to create a mechanical drawing or paste up of a whole page. A large film negative of the page is shot and used to make plates for offset printing . The next generation of phototypesetting machines to emerge were those that generated characters on a cathode-ray tube display. Typical of

7242-429: 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 typographical systems. 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 Unix troff ,

7344-421: 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. He planned to finish it on his sabbatical in 1978, but as it happened, the language was not " frozen " (ready to use) until 1989, more than ten years later. Guy Steele happened to be at Stanford during the summer of 1978, when Knuth

7446-509: 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 PDF . TeX provides

7548-473: The preparation of TeX documents through its export capability. GNU TeXmacs (whose name is a combination of TeX and Emacs , although it is independent from both of these programs) is a typesetting system which is at the same time a WYSIWYG word processor . SILE borrows some algorithms from TeX and relies on other libraries such as HarfBuzz and ICU , with an extensible core engine developed in Lua . By default, SILE's input documents can be composed in

7650-430: The previously favored 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 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

7752-542: The process took place after the printing: after cleaning with a solvent the expensive sorts had to be redistributed into the typecase - called sorting or dissing - so they would be ready for reuse. Errors in sorting could later produce misprints if, say, a p was put into the b compartment. The diagram at right illustrates a cast metal sort: a face, b body or shank, c point size, 1 shoulder, 2 nick, 3 groove, 4 foot. Wooden printing sorts were used for centuries in combination with metal type. Not shown, and more

7854-500: The reasons for the complexity of the rules of word-breaking is that different dialects of English tend to differ on hyphenation: American English tends to work on sound, but British English tends to look to the origins of the word and then to sound. There are also a large number of exceptions, which further complicates matters. Some rules of thumb can be found in the Major Keary's "On Hyphenation – Anarchy of Pedantry." Among

7956-411: The rendering of radicals has also been criticized. The OpenType math font specification largely borrows from TeX, but has some new features/enhancements. In comparison with manual typesetting, the problem of 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

8058-541: The resulting lines. If the paragraph contains n {\displaystyle n} possible breakpoints, the number of situations that must be evaluated naively is 2 n {\displaystyle 2^{n}} . However, by using the method of dynamic programming , the complexity of the algorithm can be brought down to O ( n 2 ) {\displaystyle O(n^{2})} (see Big O notation ). Further simplifications (for example, not testing extremely unlikely breakpoints such as

8160-421: The results across different computer hardware, and includes a real, Turing-complete programming language, following intense lobbying by Guy Steele. In 1989, Donald Knuth released new versions of TeX and Metafont . Despite his desire to keep the program stable, Knuth realised that 128 different characters for the text input were not enough to accommodate foreign languages; the main change in version 3.0 of TeX

8262-404: 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

8364-444: 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 π , at which point all remaining bugs will become features. Likewise, versions of Metafont after 2.0 asymptotically approach e (currently at 2.7182818), and a similar change will be applied after Knuth's death. Since

8466-644: 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. Display mathematics (mathematics presented centered on a new line) is similar but uses $ $ instead of a single $ symbol. For example, the above with the quadratic formula in display math: (The examples here are not actually rendered with TeX; spacing, character sizes, and all else may differ.) The TeX software incorporates several aspects that were not available, or were of lower quality, in other typesetting programs at

8568-464: 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 fonts were no longer available. When Knuth received the galley proofs 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

8670-456: 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 ' "). The American Mathematical Society tried in the early 1980s to claim

8772-523: 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 project was developed after 1991, primarily to enhance TeX's multilingual typesetting abilities. Knuth created "unofficial" modified versions, such as TeX-XeT , which allows

8874-475: The spoken syllables are also the basis of syllabification in writing. However, possibly due to the weak correspondence between sounds and letters in the spelling of modern English, written syllabification in English is based mostly on etymological or morphological , instead of phonetic , principles. For example, it is not possible to syllabify "learning" as lear-ning according to the correct syllabification of

8976-455: 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 1 c 4 l 4 , 1 cy, 1 d 4 i 3 a, 4 edi, e 3 dia, 2 i 1 a, ope 5 d, 2 p 2 ed, 3 pedi, pedia 4 , y 1 c. For each position in

9078-451: The syntax of the call. It differs with most widely used lexical preprocessors like 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. The original source code for the current TeX software is written in WEB , a mixture of documentation written in TeX and

9180-416: The system must pass a test suite called the TRIP test before being allowed to be called TeX. The question of license is somewhat confused by the statements included at the beginning of the TeX source code, which indicate that "all rights are reserved. Copying of this file is authorized only if ... you make absolutely no changes to your copy". This restriction should be interpreted as a prohibition to change

9282-416: 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. Since the primary goal of the TeX language is high-quality typesetting for publishers of books, Knuth gave

9384-646: The type were the Alphanumeric APS2 (1963), IBM 2680 (1967), I.I.I. VideoComp (1973?), Autologic APS5 (1975), and Linotron 202 (1978). These machines were the mainstay of phototypesetting for much of the 1970s and 1980s. Such machines could be "driven online" by a computer front-end system or took their data from magnetic tape. Type fonts were stored digitally on conventional magnetic disk drives. Computers excel at automatically typesetting and correcting documents. Character-by-character, computer-aided phototypesetting was, in turn, rapidly rendered obsolete in

9486-542: The typographic ability or flexibility required for complicated book layout, graphics, mathematics, or advanced hyphenation and justification rules ( H and J ). By 2000, this industry segment had shrunk because publishers were now capable of integrating typesetting and graphic design on their own in-house computers. Many found the cost of maintaining high standards of typographic design and technical skill made it more economical to outsource to freelancers and graphic design specialists. The availability of cheap or free fonts made

9588-573: The word, TeX will calculate the maximum value obtained among all matching patterns, yielding en 1 cy 1 c 4 l 4 o 3 p 4 e 5 d 4 i 3 a 4 . Finally, the acceptable positions are those indicated by an 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 2 i 1 a), with low indicative numbers (either odd or even), which can then be superseded by more specific patterns (such as 1 d 4 i 3 a) if necessary. These patterns find about 90% of

9690-484: 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. 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,

9792-521: Was a SCRIPT variant developed at IBM in the 1980s. DWScript is a version of SCRIPT for MS-DOS, named after its author, D. D. Williams, but was never released to the public and only used internally by IBM. Script is still available from IBM as part of the Document Composition Facility for the z/OS operating system. The standard generalized markup language ( SGML ) was based upon IBM Generalized Markup Language (GML). GML

9894-631: Was a set of macros on top of IBM Script. DSSSL is an international standard developed to provide a stylesheets for SGML documents. XML is a successor of SGML. XSL-FO is most often used to generate PDF files from XML files. The arrival of SGML/XML as the document model made other typesetting engines popular. Such engines include Datalogics Pager, Penta, Miles 33's OASYS, Xyvision's XML Professional Publisher , FrameMaker , and Arbortext . XSL-FO compatible engines include Apache FOP , Antenna House Formatter , and RenderX 's XEP . These products allow users to program their SGML/XML typesetting process with

9996-640: 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. For later versions of TeX, Knuth invented

10098-556: Was documented in the May 1975 issue of the Computing Centre Newsletter, which noted some the advantages of using SCRIPT: The article also pointed out SCRIPT had over 100 commands to assist in formatting documents, though 8 to 10 of these commands were sufficient to complete most formatting jobs. Thus, SCRIPT had many of the capabilities computer users generally associate with contemporary word processors. SCRIPT/VS

10200-499: 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. 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 The Bank of San Serriffe instead. TeX

10302-460: Was then fed to control a casting machine. The Ludlow Typograph involved hand-set matrices, but otherwise used hot metal. By the early 20th century, the various systems were nearly universal in large newspapers and publishing houses. Phototypesetting or "cold type" systems first appeared in the early 1960s and rapidly displaced continuous casting machines. These devices consisted of glass or film disks or strips (one per font ) that spun in front of

10404-419: Was typed a second time. If the two lines were identical a bell rang and the machine produced a punched paper tape corresponding to the text. With the completion of a block of lines the typesetter fed the corresponding paper tapes into a phototypesetting device that mechanically set type outlines printed on glass sheets into place for exposure onto a negative film . Photosensitive paper was exposed to light through

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