. World wide web is collection of millions of files stored on thousands of servers all over the world. These files represent documents, pictures, video, sounds, programs, interactive environments.
Following are hardware, software and protocols that make up the web.
A web server is a computer connected to the Internet that runs a program that takes responsibility for storing, retrieving and distributing some of the web files. A web client (web browser) is a computer that requests files from the web.
Well-defined set of languages and protocols that are independent of the hardware or operating system are required to run on the computers.
The Hype Text Markup Language (HTML) is the universal language of the
Java is a language for sending small applications over the web. Java script is a language for extending HTML to embed small programs called scripts in web pages. The main purpose of Java and scripts is to speed up the interactivity of web pages.
VB script and Activex controls are microsoft system that work with IE 6. Pictures, drawings, charts and diagrams are displayed on web uning image
formats such as JPEG and GIF formats.
The Virtual Reality Modeling Language (VRML) is the web’s way of describing three-dimensional objects.
A web page is an HTML document that is stored on a web server. A web site is a collection of web pages belonging to a particular organization.
URL of these pages share a common prefix, which is the address of the home page of the size. Search engines are a bottom-up approach for finding your way around the web. Some search engines search only the titles of web pages. While other search every word. Keywords can be combined with Boolean operations. such as AND, OR and NOT, to produce rather complicated queries
Home page is the front door of a web site. When a person or organization says “My web site is at to which they refer is the URI of the site’s home page. The home page introduces the rest of the web site and provides links that leads to other pages on the site.
A web browser is a program. Web browser is used to communicate with web servers on the Internet, which enables it to download and display the webpages. Netscape Navigator and Microsoft Internet Explorer are the most popular browser softwares available in market. Browser interact with web as well as computer operating system and with other programs.
Internet explorer is the default browser in newly installed window 98 systems Most browser windows have the same basic layout. Some of the basic elements
Address or location window
Some web pages are divided into independent pages, called frames.
The purpose of the web browser is to display web pages, which may either arrive over the Internet. Web browser can be used to view files of any common web format that are stored on the user system. Window, Macintosh and some Unix desktops support the default web browser.
There are different ways for opening the web page. 1. Enter its URL into the address or location box of a web browser.
2. Select it from the list that drops down from the address.
3. Link to it from another web page.
4. Link to it from a mail message or newsgroup article
Working of WWW
www uses client-server interaction. The browser program acts as a client that uses the Internet to contact a remote server for a copy of the requested page. The server on the remote system returns a copy of the page along with the additional information.
The additional information a www server returns tells the browser two important things.
1) It describes how to display the information.
2) It gives a URL for each selectable item on the page.
When a browser receives a page from a remote server, it displays the page and then waits for the user to select one of the highlighted items. Once a user makes a selection, the browser consults the hidden information that arrived with the page to find the URL that corresponds to the selection. The browser then uses the Internet to obtain the newly selected page of information.
hypermedia information retrieval initiative. It i an information system that links data from many different Internet services under one set of protocols . Web clients, called browsers, interpret Hyper Text Markup Language document
delivered from web servers.
The world wide web is a distributed, multimedia, hyper est system distributed since information on the web can be located on any computer sem connected to the Internet around the world.
It is multimedia because the information it holds can be in the form t graphics, sound and video.
Hyper text means that the information is available using hyper test technique which involves selecting highlighted phrases or images that one selected retrieve information related to the selected highlighted subject.
The information being retrieved can be information located any where in the world. The normal way to provide information on the world wide web is by writing documents in HTML. (Hyper Text Markup Language
The web is basically stateless. There is no concept of a login session. The browser sends a request to a server and gets back a file. Then the server forgets that it has ever seen that particular client.
When a client requests a web page, the server can supply additional information along with the requested page. This information may include a cookie, which wa small file. Browsers store offered cookies in a cookies directory on the client’s hard disk unless the user has disabled cookies.
way • Cookies are just files or strings, not executable programs. In principle, a ce could contain a virus, but since cookies are treated as data there is no official for the virus to actually run and do damage.
cookie may contain upto five fields.
Domain: It tells where the cookies came from. Browsers are supposed to check that servers are not lying about their domain. Each domain may store no more than 20 cookies per client.
Path: The path is a path in the server’s directory structure that identifies which parts of the server’s file tree may use the cookie. It is often 1, which mean the whole tree.
Content: It takes the form name= value. Both name and value can be anything the server wants. This field is where the cookies content is stored
Expires: The expires field specifies when the cookies expires. If this field is absent. the browser discards the cookies when it exits. Such a cookies is called a nonpersistent cookie. If a time and date are supplied, the cookie is said to persistent and is kept until it expires:
Secure: This field can be set to indicate that the browser may only return the cookie to a secure server. This feature is used for e-commerce, banking and other secure applications.
Static Web Documents
Hyper Text Markup Language (HTML) is intended as a common medium for typing together information from widely different sources. HTML documents are the Standard Generalized Markup Language (SGML) documents with generic semantic that are appropriate for representing information from a wide range of applications.
.HTML documents are in plain text format that contain embedded HTML tags: Documents can be created in any text editor. There are also many other tools. including editors, designed specifically to assist in creating HTML documents. To view an HTML document, the user needs a browser. HTML
.HTML defines the structural elements in a document such as headers, and addresses, layout information and the use of inline graphics together with the ability to provide hyper text links. Web pages were written in HTML. level
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