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
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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