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markup language is a system for annotating a text in a way which is syntactically distinguishable from that text. Examples include revision instructions by editors, traditionally written with a blue pencil on authors' manuscripts, typesetting instructions such those found in troff and LaTeX, and structural markers such as XML tags. Markup is typically omitted from the version of the text which is displayed for end-user consumption. Some markup languages, like HTML have presentation semantics, meaning their specification prescribes how the structured data is to be presented, but other markup languages, like XML, have no predefined semantics.
A well-known example of a markup language in widespread use today is HyperText Markup Language (HTML), one of the document formats of the World Wide Web. HTML is mostly an instance of SGML (though, strictly, it does not comply with all the rules of SGML) and follows many of the markup conventions used in the publishing industry in the communication of printed work between authors, editors, and printers.
Types of Electronic Markup:::There are three general categories of electronic markup: Presentational, procedural, and descriptive.Presentational markup is that used by traditional word-processing systems, binary codes embedded in document text that produced the WYSIWYG effect. Such markup is usually designed to be hidden from human users, even those who are authors or editors.Procedural markup is embedded in text and provides instructions for programs that are to process the text. Well-known examples include troff, LaTeX, and PostScript; it is expected that the processor runs through the text from beginning to end, following the instructions as encountered. Text with such markup is often edited with the markup visible and directly manipulated by the author. Popular procedural-markup systems usually include programming constructs, such that macros or subroutines can be defined and invoked by name. An example of descriptive markup would be the troff's .bd, which instructs the processor to switch to a bold-face font.In Descriptive markup, the markup is used to label parts of the document rather than to provide specific instructions as to how they should be processed. The objective is to decouple the inherent structure of the document from any particular treatment or rendition of it. Such markup is often described as "semantic". An example of descriptive markup would be HTML's
tag, which is used to label a citation.There is considerable blurring of the lines between the types of markup. In modern word-processing systems, presentational markup is often saved in descriptive-markup-oriented systems such as XML, and then processed procedurally by implementations. The programming constructs in descriptive-markup systems such as TeX may be used to create higher-level markup systems which are more descriptive, such as LaTeX.In recent years, a number of small and largely unstandardized markup languages have been developed to allow authors to create formatted text via web browsers, for use in wikis and web forums. The markup language used by Wikipedia is one such.
History
The term markup is derived from the traditional publishing practice of "marking up"' a manuscript, which involves adding handwritten annotations in the form of conventional symbolic printer's instructions in the margins and text of a paper manuscript or printed proof. For centuries, this task was done primarily by skilled typographers known as "markup men"[3] or "copy markers"[4] who marked up text to indicate what typeface, style, and size should be applied to each part, and then passed the manuscript to others for typesetting by hand. Markup was also commonly applied by editors, proofreaders, publishers, and graphic designers, and indeed by document authors.
[edit]GenCode
The idea of using markup languages in computer text processing was probably first publicly presented by publishing executive William W. Tunnicliffe at a conference in 1967, although he preferred to call it "generic coding." It can be seen as a response to the emergence of programs such as RUNOFF that each used their own control notations, often specific to the target typesetting device. In the 1970s, Tunnicliffe led the development of a standard called GenCode for the publishing industry and later was the first chair of the International Organization for Standardization committee that created SGML, the first standard descriptive markup language. Book designer Stanley Rice published speculation along similar lines in 1970.[5] Brian Reid, in his 1980 dissertation at Carnegie Mellon University, developed the theory and a working implementation of descriptive markup in actual use.
However, IBM researcher Charles Goldfarb is more commonly seen today as the "father" of markup languages. Goldfarb hit upon the basic idea while working on a primitive document management system intended for law firms in 1969, and helped invent IBM GML