Friday 28 November, 2008
Introduction to Scripting language Web Browser etc
Scripting Language
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A scripting language, script language or extension language, is a programming language that allows some control of a single or many software application(s). "Scripts" are often treated as distinct from "programs", which execute independently from any other application. At the same time they are distinct from the core code of the application, which is usually written in a different language, and by being accessible to the end user they enable the behavior of the application to be adapted to the user's needs. Scripts are often, but not always, interpreted from the source code or "semi-compiled" to byte code which is interpreted, unlike the applications they are associated with, which are traditionally compiled to native machine code for the system on which they run. Scripting languages are nearly always embedded in the application with which they are associated.
The name "script" is derived from the written script of the performing arts, in which dialogue is set down to be spoken by human actors. Early script languages were often called batch languages or job control languages. Such early scripting languages were created to shorten the traditional edit-compile-link-run process.
Web browsers
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Main article: Client-side scripting
Web browsers are typically used to render HTML, but in time a host of special-purpose languages has developed to control their operation. These include ECMAScript, a very versatile procedural scripting language superficially resembling Java; Cascading style sheets, which enable style metadata to be abstracted from content; XML which can be used for content in conjunction with style metadata, as an alternative to HTML; and XSLT, a presentation language that transforms XML content into a new form. Techniques involving the combination of XML and JavaScript scripting to improve the user's subjective impression of responsiveness have become significant enough to acquire a name: AJAX. The Document Object Model standard ensures that all browsers respond in a predictable manner to the same JavaScript.
The Mozilla project has developed its own system for extending the user interface of the browser itself, called XUL.
Web servers
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On the server side of the HTTP link, application servers and other dynamic content servers such as Web content management systems provide content through a large variety of techniques and technologies typified by the scripting approach. Particularly prominent in this area are PHP, Coldfusion and ASP, but other developments such as Ruby on Rails have carved out a niche.
Text processing languages
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The processing of text-based records is one of the oldest uses of scripting languages. Many, such as Unix's awk, sed, and grep were originally designed to aid programmers in automating tasks that involved Unix text-based configuration and log files. Of primary importance here is the regular expression, a language developed for the formal description of the lexical structure of text, and used by all of these tools.
Perl was originally designed to overcome the limitations of these tools, but has grown to be one of the most widespread general purpose scripting languages.
General-purpose dynamic languages
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Some languages, such as Perl, began as scripting languages but were developed into programming languages suitable for broader purposes. Other similar languages – frequently interpreted, memory-managed, or dynamic – have been described as "scripting languages" for these similarities, even if they are more commonly used for applications programming. They are usually not called "scripting languages" by their own users.
introduction to html (must read article)
Introduction to html
Markup
--------------
Markup is the information that is added to a document to convey information about the documents structure or presentation . markup languages are all arround us in everyday computing. while you may not see it , word processing document are filled with html code indicating the structure and presentation of the document . (what you see on your screen just looks like a page of text) but the formatting is done "behind the scenes"
by the markup(HTML) and its successor,XHTML, are the not so behind the scenes markup language that are used to tell web browser how to structure and some may say display web pages.
HTML
----------------
HTML (HyperText Markup Language) is the predominant markup language for Web pages. It provides a means to describe the structure of text-based information in a document — by denoting certain text as links, headings, paragraphs, lists, and so on — and to supplement that text with interactive forms, embedded images, and other objects. HTML is written in the form of tags, surrounded by angle brackets. HTML can also describe, to some degree, the appearance and semantics of a document, and can include embedded scripting language code (such as JavaScript) which can affect the behavior of Web browsers and other HTML processors.
Extension of html pages is html or htm.
Origins
--------------
Tim Berners-LeeIn 1980,
physicist Tim Berners-Lee,
who was an independent contractor at CERN, proposed and prototyped ENQUIRE, a system for CERN researchers to use and share documents. In 1989, Berners-Lee and CERN data systems engineer Robert Cailliau each submitted separate proposals for an Internet-based hypertext system providing similar functionality. The following year, they collaborated on a joint proposal, the WorldWideWeb (W3) .
First specifications
-------------------------------
The first publicly available description of HTML was a document called HTML Tags, first mentioned on the Internet by Berners-Lee in late 1991. It describes 22 elements comprising the initial, relatively simple design of HTML. Thirteen of these elements still exist in HTML 4.
Berners-Lee considered HTML to be, at the time, an application of SGML(standard generalized markup language), but it was not formally defined as such until the mid-1993 publication, by the IETF(internet engineering task force), of the first proposal for an HTML specification: Berners-Lee and Dan Connolly's "Hypertext Markup Language (HTML)" Internet-Draft, which included an SGML Document Type Definition to define the grammar.[5] The draft expired after six months, but was notable for its acknowledgment of the NCSA Mosaic browser's custom tag for embedding in-line images, reflecting the IETF's philosophy of basing standards on successful prototypes.[6] Similarly, Dave Raggett's competing Internet-Draft, "HTML+ (Hypertext Markup Format)", from late 1993, suggested standardizing already-implemented features like tables and fill-out forms.
After the HTML and HTML+ drafts expired in early 1994, the IETF created an HTML Working Group, which in 1995 completed "HTML 2.0", the first HTML specification intended to be treated as a standard against which future implementations should be based.[6] Published as Request for Comments 1866, HTML 2.0 included ideas from the HTML and HTML+ drafts.[8] There was no "HTML 1.0"; the 2.0 designation was intended to distinguish the new edition from previous drafts.
Further development under the auspices of the IETF was stalled by competing interests. Since 1996, the HTML specifications have been maintained, with input from commercial software vendors, by the World Wide Web Consortium (W3C).[10] However, in 2000, HTML also became an international standard . The last HTML specification published by the W3C is the HTML 4.01 Recommendation, published in late 1999. Its issues and errors were last acknowledged by errata published in 2001.
Markup
--------------
Markup is the information that is added to a document to convey information about the documents structure or presentation . markup languages are all arround us in everyday computing. while you may not see it , word processing document are filled with html code indicating the structure and presentation of the document . (what you see on your screen just looks like a page of text) but the formatting is done "behind the scenes"
by the markup(HTML) and its successor,XHTML, are the not so behind the scenes markup language that are used to tell web browser how to structure and some may say display web pages.
HTML
----------------
HTML (HyperText Markup Language) is the predominant markup language for Web pages. It provides a means to describe the structure of text-based information in a document — by denoting certain text as links, headings, paragraphs, lists, and so on — and to supplement that text with interactive forms, embedded images, and other objects. HTML is written in the form of tags, surrounded by angle brackets. HTML can also describe, to some degree, the appearance and semantics of a document, and can include embedded scripting language code (such as JavaScript) which can affect the behavior of Web browsers and other HTML processors.
Extension of html pages is html or htm.
Origins
--------------
Tim Berners-LeeIn 1980,
physicist Tim Berners-Lee,
who was an independent contractor at CERN, proposed and prototyped ENQUIRE, a system for CERN researchers to use and share documents. In 1989, Berners-Lee and CERN data systems engineer Robert Cailliau each submitted separate proposals for an Internet-based hypertext system providing similar functionality. The following year, they collaborated on a joint proposal, the WorldWideWeb (W3) .
First specifications
-------------------------------
The first publicly available description of HTML was a document called HTML Tags, first mentioned on the Internet by Berners-Lee in late 1991. It describes 22 elements comprising the initial, relatively simple design of HTML. Thirteen of these elements still exist in HTML 4.
Berners-Lee considered HTML to be, at the time, an application of SGML(standard generalized markup language), but it was not formally defined as such until the mid-1993 publication, by the IETF(internet engineering task force), of the first proposal for an HTML specification: Berners-Lee and Dan Connolly's "Hypertext Markup Language (HTML)" Internet-Draft, which included an SGML Document Type Definition to define the grammar.[5] The draft expired after six months, but was notable for its acknowledgment of the NCSA Mosaic browser's custom tag for embedding in-line images, reflecting the IETF's philosophy of basing standards on successful prototypes.[6] Similarly, Dave Raggett's competing Internet-Draft, "HTML+ (Hypertext Markup Format)", from late 1993, suggested standardizing already-implemented features like tables and fill-out forms.
After the HTML and HTML+ drafts expired in early 1994, the IETF created an HTML Working Group, which in 1995 completed "HTML 2.0", the first HTML specification intended to be treated as a standard against which future implementations should be based.[6] Published as Request for Comments 1866, HTML 2.0 included ideas from the HTML and HTML+ drafts.[8] There was no "HTML 1.0"; the 2.0 designation was intended to distinguish the new edition from previous drafts.
Further development under the auspices of the IETF was stalled by competing interests. Since 1996, the HTML specifications have been maintained, with input from commercial software vendors, by the World Wide Web Consortium (W3C).[10] However, in 2000, HTML also became an international standard . The last HTML specification published by the W3C is the HTML 4.01 Recommendation, published in late 1999. Its issues and errors were last acknowledged by errata published in 2001.
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