A web server
is basically specialized software running on a computer, often no more powerful
than the desktop variety. In fact, virtually any computer can run web server software.
Both the Mac and the PC come with personal versions of web server software. The
web server understands requests made from "clients" (visitors using
a web browser) and presents requested HTML files along with images and other specialized
content to the browser for viewing.
All web servers can handle standard
HTML files, images in standard web formats (GIF, JPG, and often PNG), and with
correct settings on the server rich media files like Flash, Quicktime, and Shockwave.
All common web servers also have the ability to run scripts for processing data
and a variety of functions. The language "Perl" is probably the most
common and is available on most web servers. Javascript is widely known and very
widely used but it is a "client side" scripting language because it
is not processed by the server but rather by the browser. Perl requires that the
script be processed by the server.
There are several other important technologies
that can be implemented on a web server and perform important functions such as
accessing a database and running a shopping cart to name but a few. Three of the
most common are PHP, ASP, and Cold Fusion. You might think of them as competitors
in the higher end server functionality game and all require a knowledge of how
to write scripts in the different languages, but they all differ in the way they
are made available.
PHP is open source and therefore is free. It is typically
installed on the machine running the web server and then processes the PHP tags
that are written into a standard HTML document. There are installations of PHP
written for most common platforms and you know you are on a page using PHP by
the suffix ".php". ASP (Active Server Pages) is a Microsoft invention
and originally required a Microsoft server to be able to to make use of it. The
actual scripting for ASP is written in either Javascript or VBscript. You can
tell you are on a site using asp page by the ".asp" suffix but if you
view the source of an ASP page, you will see only standard HTML. The server has
processed the page, doing whatever dynamic tasks were called for and displayed
the results as plain HTML. It is now possible to run ASP technology on non-Microsoft
servers with Chilisoft ASP which essentially duplicates most of the operations
of the Microsoft implementation. The last, Cold Fusion, seen by the ".cfm"
suffix on a ColdFusion enabled server, is a proprietary language and server combination
that is now owned by Macromedia. Essentially, all of these technologies extend
the functionality of good 'ol HTML by providing database access and a wealth of
dynamic page processing features. There can be much more to the web today than
a static page.
