What is HTML?
HTML, or HyperText Markup Language, is a platform-independent, open standard for transmitting many types of data online. The most common application of HTML is in the creation of documents published on the WWW (World Wide Web)
The purpose of this page is to describe what HTML is by briefly analyzing and clarifying what one means by the terms "Hypertext", "Markup" and "Language" in the context of HTML.
HTML is a language. It has several features in common with human languages. For example it has a lexicon and a syntax. That is, it has a variety of "vocabulary items" as well as rules for using them. Its set of lexical items is quite limited and not open to arbitrary expansion. Furthermore, unlike human languages, it is quite unambiguous. Each item has a specific meaning and can be used only in certain ways. Elements of HTML are encompassed by starting and ending brackets, the < and > signs. HTML is not case-sensitive; <P> and <p> are the same. Many such items, called "tags", can be "modified" by optional parameters. For example a paragraph <p> can be either left-, right- or center- aligned (<p align=left>, <p align=right>, <p align=center>). If no modifier is given, a default value is assumed (by default, paragraphs are left-justified).
HTML is a Markup language. Markup languages are used for formatting and describing the structure of documents, especially plain text. Certain tags are placed around elements of the text, and these tags are then interpreted by a program such as Netscape Navigator, which uses these tags to format the text and graphics on your screen. For example, such tags are used to tell Netscape to make some text bold, other italic, or to format some text into a list or table.
A markup language is different from computer programming languages such as Java or C in several ways. For instance, a markup language is not used to create a program. HTML does not have any "fuctions" and does provide any "commands", it merely describes how a text is organized.
Finally, in contrast to a desktop publishing program or page layout program, a markup language should be used to describe the logical organization of a document rather than its physical presentation. That is, in a given document, a piece of text should be described as a "header", a "paragraph", or "list item". Physical layout is concerned with making text bold or italic; logical markup instead labels data according to its function; is it "emphasized" or "strong"? The choice of how to physically present a certain type of logical markup should be left to the client program, such as Navigator or Internet Explorer.
HTML marks up hypertext. In contrast to typical "linear" documents, HTML provides a way to present non-linear, hypertext documents. Parts of a document (text, a graphic, etc.) can be linked to other documents or parts of other documents. For example, the online version of a book can provide links at he bottom of a page to the previous and following pages. Links in an online encyclopedia, catalog or other reference work can be cross-referenced with similar concepts in other documents. Hypertext links can also be used to link to documents on other "sites". Such links are given by a standardized addressing system. For example, links to other web-sites are prefixed by "http://", documents on FTP servers are prefixed by "ftp://" and links to telnet servers are prefixed by "telnet://". The address for a site is then given in the form of a URL, or Uniform Resource Locator. Local documents (on the same computer as the starting document) can be referenced simply by a filename.
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