Page 12 - DCAP408_WEB_PROGRAMMING

Web Programming

Notes Web browsers talk with web servers using HTTP (hypertext transfer protocol) to retrieve web pages.
HTTP enables web browsers to provide information to web servers to retrieve web pages from
them. Different web pages have a URL address starting with http:// for HTTP access. There may
different other URL types and their corresponding protocols and most of the browsers supports
them. FTP (file transfer protocol) is one of the examples of such types. Other examples are rtsp: for
RTSP (real-time streaming protocol) and https: for HTTPS (an SSL encrypted version of HTTP).
The file format for a Web page is normally HTML (hyper-text markup language) and is identified
in the HTTP protocol with a MIME content type. Most of the browsers support different formats
such as the JPEG, PNG and GIF image formats including HTML. The combination of HTTP content
type and URL protocol specification enables designers to embed images, animations, video, sound
and streaming media into a web page or to make them accessible through the web page.

Like much of the internet, the World Wide Web operates on a client/server model. You run a Web
client on your computer — called a Web browser — such as Netscape Communicator or Microsoft’s
Internet Explorer. That client contacts a Web server and requests information or resources. The
Web server locates and then sends the information to the Web browser, which displays the results.
When Web browsers contact servers, they are asking to view pages built with Hypertext Markup
Language (HTML). They interpret those pages and display them on your computer. They display
application programs, animations, and similar material created with programming languages
such as Java and ActiveX, and scripting languages such as JavaScript. Sometimes, home pages
contain links to files that the Web browser cannot play or display, such as sound or animation files.
In that case, you will need a plug-in or a helper application.

Task You configure your Web browser to use the helper application or plug-in whenever
it encounters a sound or animation file that the browser cannot run or play. Analyze this
statement practically.
Over the years, Web browsers have become increasingly sophisticated. They have become full-
blown software suites that can do everything from video-conferencing to letting you create and
publish HTML pages. They have also begun to blur the line between your local computer and
the Internet-in essence, they can make your computer and the Internet function as a single
system. To facilitate the usage of computers over Internet, Microsoft has integrated web browsing
and the Internet directly into the operating system. For example, with Internet Explorer 4.0 and
above, and with Windows 98, the Windows desktop can be HTML based. This means Web links
can be directly embedded into the desktop.
So, you can have links to your favourite Web pages right on the desktop. And even applications
such as word processors now have Web capabilities bust into them — such as being able to browse
the Web, or build home pages. Even more significantly, using technology that Microsoft calls
Active Desktop, internet based desktop components can live on the desktop. These components
can be things such as stock tickers, which deliver live Web content directly to the desktop. You
don’t need to fire up your Web browser to get the information; it’s delivered straight to your
Windows desktop without your having to do anything. Both Microsoft and Netscape have also
built entire suites of software around their browsers. Netscape for example, calls its suite Netscape
Communicator. Communicator includes modules for reading newsgroups; for reading, sending
and managing internet mail; for audio conferencing; for collaborative work on whiteboard
applications in which people can view and mark up the same documents simultaneously; and
more. These enhancements will help user in an era of collaborative computing and communication.

 It allows you to enter the address of the site you want to jump to (called a URL-or uniform
resource locator), or to jump there by clicking hotspots, high lighted words, buttons,
pictures, or icons called hyperlinks on your screen.

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