Hyperlink
In computing, a hyperlink (or link) is a reference to a document that the reader can directly follow, or that is followed automatically. The reference points to a whole document or to a specific element within a document. Hypertext is text with hyperlinks. Such text is usually viewed with a computer. A software system for viewing and creating hypertext is a hypertext system. To hyperlink (or simply to link) is to create a hyperlink. A user following hyperlinks is said to navigate or browse the hypertext.
A hyperlink has an anchor, which is a location within a document from which the hyperlink can be followed; that document is known as its source document. The target of a hyperlink is the document, or location within a document, that the hyperlink leads to. The user can follow the link when its anchor is shown by activating it in some way (often, by touching it or clicking on it with a pointing device). Following has the effect of displaying its target, often with its context.
In some hypertext, hyperlinks can be bidirectional: they can be followed in two directions, so both points act as anchors and as targets. More complex arrangements exist, such as many-to-many links.
The most common example of hypertext today is the World Wide Web: webpages contain hyperlinks to webpages. For example, in an online reference work such as Wikipedia, many words and terms in the text are hyperlinked to definitions of those terms. Hyperlinks are often used to implement reference mechanisms that predate the computer, such as tables of contents, footnotes, bibliographies, indexes and glossaries.
The effect of following a hyperlink may vary with the hypertext system and sometimes on the link itself; for instance, on the World Wide Web, most hyperlinks cause the target document to replaces the document being displayed, but some are marked to cause the target document to open in a new window. Another possibility is transclusion, for which the link target is a document fragment that replaces the link anchor within the source document. A third option exists when an automatic software program traverses the hypertext following each hyperlink and gathering all the retrieved documents. That program is said to be spidering or crawling the hypertext.
Types of links
External links
The word example in this sentence is a hyperlink that points to a different (external document) – if the word is clicked, the browser will navigate to a different page. Such links are called navigation links or external links.
Inline link
An inline link displays remote content without the need for embedding the content. The remote content may be accessed with or without the user selecting the link. For example, the image above is a document that can be viewed separately, but it is included into this page with an inline link.
A inline link may display a modified version of the content; for instance, instead of an image, a thumbnail, low resolution preview, cropped section, or magnified section. The full content will then usually be available on demand, as is the case with print publishing software – e.g. with an external link. This allows for smaller file sizes and quicker response to changes when the full linked content is not needed, as is the case when rearranging a page layout.
Hot area
A hot area (image map in HTML) is a hyperlink anchor formed by a designated, often irregular part of an image or of other content. One way to define it is by a list of coordinates that indicate its boundaries. For example, a political map of Africa may have each irregularly shaped country hyperlinked to further information about that country. A separate invisible hot area interface allows for swapping skins or labels within the linked hot areas without repetitive embedding of links in the various skin elements.
Random accessed
Random-accessed linking data are links retrieved from a database or variable containers in a program when the retrieval function is from user interaction (e.g. dynamic menu from an address book) or non-interactive (e.g. random, calculated) process.
Hardware accessed
A hardware-accessed link is a link that activates directly via an input device (e.g. keyboard, microphone, remote control) without the need or use of a graphical user interface.
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