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TeX, stylized within the system as X, is a typesetting system which was designed and written by Donald Knuth and first released in 1978.

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TeX, stylized within the system as X, is a typesetting system which was designed and written by Donald Knuth and first released in 1978.

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TeX is a popular means of typesetting complex mathematical formulae; it has been noted as one of the most sophisticated digital typographical systems.

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TeX is widely used in academia, especially in mathematics, computer science, economics, political science, engineering, linguistics, physics, statistics, and quantitative psychology.

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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.

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TeX is free software, which made it accessible to a wide range of users.

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TeX planned to finish it on his sabbatical in 1978, but as it happened, the language was not "frozen" until 1989, more than ten years later.

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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.

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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.

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TeX82 uses fixed-point arithmetic instead of floating-point, to ensure reproducibility of the results across different computer hardware, and includes a real, Turing-complete programming language, following intense lobbying by Guy Steele.

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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.

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Since the source code of TeX is essentially in the public domain, other programmers are allowed to improve the system, but are required to use another name to distribute the modified TeX, meaning that the source code can still evolve.

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Many thousands of books have been published using TeX, including books published by Addison-Wesley, Cambridge University Press, Elsevier, Oxford University Press, and Springer.

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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.

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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.

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Nowadays, pdfTeX is often used, which bypasses DVI generation altogether.

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The most widely used format is LaTeX, originally developed by Leslie Lamport, which incorporates document styles for books, letters, slides, etc.

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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.

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TeX 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 under the supervision of Hans Wolf; editions of the mathematical journal Acta Mathematica dating from around 1910; and a copy of Indagationes Mathematicae, a Dutch mathematics journal.

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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.

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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.

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TeX82 introduced a new hyphenation algorithm, designed by Frank Liang in 1983, to assign priorities to breakpoints in letter groups.

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For each position in the word, TeX will calculate the maximum value obtained among all matching patterns, yielding en1cy1c4l4o3p4e5d4i3a4.

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Metafont, not strictly part of TeX, is a font description system which allows the designer to describe characters algorithmically.

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TeX documents are written and programmed using an unusual macro language.

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Original source code for the current TeX software is written in WEB, a mixture of documentation written in TeX and a Pascal subset in order to ensure readability and portability.

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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.

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On UNIX-compatible systems, including Linux and Apple macOS, TeX is distributed as part of the larger TeX Live distribution.

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TeX has been the official typesetting package for the GNU operating system since 1984.

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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.

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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.

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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.

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The letters of the name are meant to represent the capital Greek letters tau, epsilon, and chi, as TeX is an abbreviation of te???, Greek for both "art" and "craft", which is the root word of technical.

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The Deutschsprachige Anwendervereinigung TeX is a large user group in Germany.

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