Friday 7 December 2012

Lecture 2 Web Browsers


Web Browsers

A web browser is a software application for retrieving, presenting, and traversing information resources on the World Wide Web. An information resource is identified by a Uniform Resource Identifier (URI) and may be a web page, image, video, or other piece of content. ...

A web browser or Internet browser is a software application for retrieving, presenting, and traversing information resources on the World Wide Web. An information resource is identified by a Uniform Resource Identifier (URI) and may be a web page, image, video, or other piece of content. Hyperlinks present in resources enable users to easily navigate their browsers to related resources.

Although browsers are primarily intended to access the World Wide Web, they can also be used to access information provided by Web servers in private networks or files in file systems. Some browsers can also be used to save information resources to file systems.

 

HISTORY OF WEB BROWSERS

WorldWideWeb for NeXT, released in 1991, was the first Web browser.

The history of the Web browser dates back in to the late 1980s, when a variety of technologies laid the foundation for the first Web browser, WorldWideWeb, by Tim Berners-Lee in 1991. That browser brought together a variety of existing and new software and hardware technologies.

Ted Nelson and Douglas Engelbart developed the concept of hypertext long before Berners-Lee and CERN. It became the core of the World Wide Web. Berners-Lee does acknowledge Engelbart's contribution.

The introduction of the NCSA Mosaic Web browser in 1993 – one of the first graphical Web browsers – led to an explosion in Web use. Marc Andreessen, the leader of the Mosaic team at NCSA, soon started his own company, named Netscape, and released the Mosaic-influenced Netscape Navigator in 1994, which quickly became the world's most popular browser, accounting for 90% of all Web use at its peak (see usage share of web browsers).

Microsoft responded with its browser Internet Explorer in 1995 (also heavily influenced by Mosaic), initiating the industry's first browser war. By bundling Internet Explorer with Windows, Microsoft was able to leverage its dominance in the operating system market to take over the Web browser market; Internet Explorer usage share peaked at over 95% by 2002. Internet Explorer has 60% browser usage share as of September 2010 according to Net Applications, and it continues to show a negative trend.

Opera first appeared in 1996; although it has never achieved widespread use, with a browser usage share that is stable around 2.4% as of September 2010,[4] it has a substantial share of the fast-growing mobile phone Web browser market, being preinstalled on over 40 million phones. It is also available on several other embedded systems, including Nintendo's Wii video game console.

In 1998, Netscape launched what was to become the Mozilla Foundation in an attempt to produce a competitive browser using the open source software model. That browser would eventually evolve into Firefox, which developed a respectable following while still in the beta stage of development; shortly after the release of Firefox 1.0 in late 2004, Firefox (all versions) accounted for 7.4% of browser use. As of September 2010, Firefox has a 23% usage share.

Apple's Safari had its first beta release in January 2003; it has a dominant share of Apple-based Web browsing, accounting for 5.3% of the entire browser market as of September 2010 and is slowly gaining. Its rendering engine, called WebKit, is also running in the standard browsers of several mobile phone platforms, including Apple iOS, Google Android, Nokia S60 and Palm web OS.

The most recent major entrant to the browser market is Google's WebKit-based Chrome, first released in September 2008. Its market share has quickly risen; as of September 2010, it has an 8% usage share and appears to be gaining further in the coming months.

Function of web browser

The primary purpose of a web browser is to bring information resources to the user. This process begins when the user inputs a Uniform Resource Identifier (URI), for example http://en.wikipedia.org/, into the browser.

The prefix of the URI determines how the URI will be interpreted. The most commonly used kind of URI starts with http: and identifies a resource to be retrieved over the Hypertext Transfer Protocol (HTTP). Many browsers also support a variety of other prefixes, such as https: for HTTPS, ftp: for the File Transfer Protocol, and file: for local files. Prefixes that the web browser cannot directly handle are often handed off to another application entirely. For example, mailto: URIs are usually passed to the user's default e-mail application and news: URIs are passed to the user's default newsgroup reader.

In the case of http, https, file, and others, once the resource has been retrieved the web browser will display it. HTML is passed to the browser's layout engine to be transformed from markup to an interactive document. Aside from HTML, web browsers can generally display any kind of content that can be part of a web page. Most browsers can display images, audio, video, and XML files, and often have plug-ins to support Flash applications and Java applets. Upon encountering a file of an unsupported type or a file that is set up to be downloaded rather than displayed, the browser prompts the user to save the file to disk.

Interactivity in a web page can also be supplied by JavaScript, which usually does not require a plugin. JavaScript can be used along with other technologies to allow "live" interaction with the web page's server via AJAX.

Information resources may contain hyperlinks to other information resources. Each link contains the URI of a resource to go to. When a link is clicked, the browser navigates to the resource indicated by the link's target URI, and the process of bringing content to the user begins again.

Features of a web browser

Available web browsers range in features from minimal, text-based user interfaces with bare-bones support for HTML to rich user interfaces supporting a wide variety of file formats and protocols. Browsers which include additional components to support e-mail, Usenet news, and Internet Relay Chat (IRC), are sometimes referred to as "Internet suites" rather than merely "web browsers".

All major web browsers allow the user to open multiple information resources at the same time, either in different browser windows or in different tabs of the same window. Major browsers also include pop-up blockers to prevent unwanted windows from "popping up" without the user's consent.

Most web browsers can display a list of web pages that the user has bookmarked so that the user can quickly return to them. Bookmarks are also called "Favorites" in Internet Explorer. In addition, all major web browsers have some form of built-in web feed aggregator. In Mozilla Firefox, web feeds are formatted as "live bookmarks" and behave like a folder of bookmarks corresponding to recent entries in the feed. In Opera, a more traditional feed reader is included which stores and displays the contents of the feed.

Furthermore, most browsers can be extended via plug-ins, downloadable components that provide additional features.

Browser User Interface

Most major web browsers have these user interface elements in common:

Ø  Back and forward buttons to go back to the previous resource and forward again.

Ø  A history list, showing resources previously visited in a list (typically, the list is not visible all the time and has to be summoned)

Ø  A refresh or reload button to reload the current resource.

Ø  A stop button to cancel loading the resource. In some browsers, the stop button is merged with the reload button.

Ø  A home button to return to the user's home page

11 comments:

  1. Wow! tomorrow is going to be the "D-Day" I wonder how the on-line test is gonna look like, I only hope and pray that it will turn out to be easier than expected.

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  4. TO THE DREAMS OF OUR HEART, TO THE PRAYERS ON OUR LIPS, TO EVERY EXPECTATIONS AND ALL THAT YOU HOPE FOR AND TO THE BEAUTIFUL FUTURE AHEAD ARE YOURS NOW AND FOREVER.

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  5. Sms/10/mac/00848
    Fatima Shehu Minjibir
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    http://fateemashehu.blogspot.co.uk/?m=1

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  6. To meet and part is d way of life but to part and meet is d will of Allah (S.W.A).

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    To meet and part is d way of life but to part and meet is d will of Allah (S.W.A).

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  9. NAME: BASIRA HAMISU IBRAHIM
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  10. I will bookmark it in my future updates.Keep it up nice post..

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