Page 199 - DCAP406_DCAP_207_Computer Networks

Computer Networks/Networks

Notes Both of the above techniques may also be used concurrently to develop dynamic
webpages. The advantages of dynamic webpages are that it enables easy update of the webpages
and faster webpage loading. In dynamic webpage, the content and design are located separately
and thus allowing frequent modifications to the web pages including text and image updates.
Active documents: The program that runs at the client side are known as the active documents.
Whenever a web client requests an active document, the web server provides a copy of the
document in the form of byte code. The document is now ready to run at the web client machine.
As the active document is served in the binary form therefore it can be applied compression and
decompression at server and client side to reduce the bandwidth requirement and throughput.

12.3.3 Hypertext Markup Language (HTML)

HTML is the standard language used by the WWW for creating and recognizing hypermedia
documents. The webpages are written in HTML code and HTML files are saved with the suffix
“.html”. The HTML documents are standard 7-bit ASCII files with formatting codes that contain
information about layouts, hyperlinks etc and users may control visual elements like fonts, font
size, paragraph spacing, etc without changing the original information. Conversion software is
used to translate documents from other formats into HTML. The documents in any language can
be presented on the web by converting them into HTML format with the help of numbers of
software available easily. There are filters available on web to convert files in RTF (Rich Text
Format), WordPerfect and FrameMaker as well as mail archives and text-only documents. The
HTML standard is used to support basic hypermedia document creation and layout. However
HTML is limited in handling many complex layout techniques found in traditional document
publishing. It can support interactive forms, defined “hot spots” in images, more versatile
layout and formatting options and styles, formatted tables, etc. HTML+ enables the user to
include an e-mail hyperlinks to send e-mail automatically in which selecting an e-mail address
in a piece of hypertext would open a mail program, ready to send e-mail to that address. The
characteristics of the HTML as a markup language is enable a user to embed formatting instructions
in the file itself, which are stored with the text so that any browser can read the file itself.

12.3.4 Uniform Resource Locators (URL)

The WWW is not possible without Uniform Resource Locators (URLs). They are used to represent
hypermedia links and links to network services within HTML documents. Any file or service on
the Internet can be presented with a URL. The first part of the URL that comes before the two
slashes is used to specify the method of access or protocol being followed for communications
between browser and web server. The second part coming after two slashes represents the address
of the host machine to which data or service is being sought. The other parts following the second
part may specify the names of files, the port to connect to or the text to search for in a database. All
the parts of an address for obtaining a file or service from a host machine in a URL are shown as a
single unbroken line with no spaces and the locations of the host machines or websites that run
www servers are typically named with a www at the beginning of the network address. In
accessing web services, the web browsers enable the user to specify a URL and connect to that
document or service. When the user gets connected with web serve, the user by selecting hypertext
in an HTML document sends a request to open a URL. Thus, hyperlinks are used not only to
provide other texts and media in the same document but also to provide other network services.
Web browsers are not simply web clients. They are full-featured FTP, Gopher and telnet clients.

Common Gateway Interface

The Common Gateway Interface (CGI) is used as a standard protocol for interfacing external
application software with a web server in which the web server responds to the request sent by

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