The World Wide Web (abbreviated as WWW or W3, commonly
known as the web), is a system of interlinked hypertext documents
accessed via the Internet. With a web browser, one can view web
pages that may contain text, images, videos, and other multimedia, and navigate between
them via hyperlinks.
Using concepts from his earlier hypertext systems
like ENQUIRE, British engineer, computer scientist and at that
time employee of the CERN, Sir Tim Berners-Lee, now Director of the World
Wide Web Consortium (W3C), wrote a proposal in March 1989 for what would
eventually become the World Wide Web. At CERN, a European research
organisation near Geneva straddling the border between France and Switzerland,
Berners-Lee and Belgian computer scientist Robert Cailliau proposed
in 1990 to use hypertext "to link and access information of various kinds
as a web of nodes in which the user can browse at will", and they
publicly introduced the project in December of the same year.
The terms Internet and World Wide Web are often
used in everyday speech without much distinction. However, the Internet and the
World Wide Web are not the same. The Internet is a global system of
interconnected computer networks. In contrast, the web is one of the
services that runs on the Internet. It is a collection of text documents and
other resources, linked by hyperlinks and URLs, usually accessed by web
browsers from web servers. In short, the web can be thought of as an application "running"
on the Internet.
Viewing a web page on the World Wide Web
normally begins either by typing the URL of the page into a web
browser or by following a hyperlink to that page or resource.
The web browser then initiates a series of communication messages, behind the
scenes, in order to fetch and display it. In the 1990s, using a browser to view
web pages and to move from one web page to another through hyperlinks came to
be known as 'browsing,' 'web surfing,' or 'navigating the web'. Early studies
of this new behavior investigated user patterns in using web browsers. One
study, for example, found five user patterns: exploratory surfing, window
surfing, evolved surfing, bounded navigation and targeted navigation.
The following example demonstrates how a web browser
works. Consider accessing a page with the URL http://example.org/wiki/World_Wide_Web.
First, the browser resolves the server-name portion of the URL (example.org)
into an Internet Protocol address using the globally distributed
database known as the Domain Name System (DNS); this lookup returns
an IP address such as 208.80.152.2. The browser then requests the resource
by sending an HTTP request across the Internet to the computer at
that particular address. It makes the request to a particular application port
in the underlying Internet Protocol Suite so that the computer
receiving the request can distinguish an HTTP request from other network
protocols it may be servicing such as e-mail delivery; the HTTP protocol
normally uses port 80. The content of the HTTP request can be as simple as
the two lines of text
GET /wiki/World_Wide_Web HTTP/1.1
Host: example.org
The computer receiving the HTTP request delivers it
to web server software listening for requests on port 80. If the web
server can fulfill the request it sends an HTTP response back to the browser
indicating success, which can be as simple as
HTTP/1.0 200 OK
Content-Type: text/html; charset=UTF-8
followed by the content of the requested page. The
Hypertext Markup Language for a basic web page looks like
<html>
<head>
<title>Example.org – The World Wide
Web</title>
</head>
<body>
<p>The World Wide Web, abbreviated as WWW
and commonly known ...</p>
</body>
</html>
The web browser parses the HTML,
interpreting the markup (<title>, <p> for paragraph, and
such) that surrounds the words in order to draw the text on the screen.
Many web pages use HTML to reference the URLs of
other resources such as images, other embedded media, scripts that
affect page behavior, and Cascading Style Sheets that affect page
layout. The browser will make additional HTTP requests to the web server for
these other Internet media types. As it receives their content from the
web server, the browser progressively renders the page onto the
screen as specified by its HTML and these additional resources.
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