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| Surf
around the web for
a while and you will
notice that some of
the web pages that
you view have different
file extensions. For
example, this web
page is titled web-page-extensions.htm.
It could have been
titled web-page-extensions.html
though. So what is
different between
all of these extensions?
Is a .asp better or
worse than a .cgi
extension? Or is everyone
just being creative? |
|
| When
your internet browser
requests a web page
from a web host it
examines the file
extension. If the
extension is hyper
text mark up language
(.htm or .html) then
it is rendered in
your browser. If the
extension is something
else then, depending
on what the extension
is, the server software
does something to
the page and then
sends you the page.
What the server software
does depends on what
is written in the
web page. And frequently
the web pages are
running programming
scripts or mini-computer
programs which are
processing data before
or after you arrive. |
|
| For
example, if you have
ever been to a web
page which displays
the IP address of
where you are (an
IP address is a numerical
address of your computer
on the internet),
chances are the web
page is a .php extension.
Why? Because using
the PHP language it
is very easy to display
this. What happens
when you request the
page with the .php
extension is that
the server software
runs a computer script
(a PHP language script
in this case) and
before the web page
is displayed in your
browser, it adds the
results of the computer
script. So the .php
extension allows a
web page to interact
dynamically with each
person visiting the
site. Thus, each time
someone visits your
php page, they will
see something different
because the IP address
of their computer
is different from
yours. |
|
| Some
of the different extensions
you will see are as
follows: |
|
| .PHP |
| (Hypertext
Preprocessor Lanugage:
Scripting language
in the web page itself) |
|
| .ASP |
| (Active
Server Pages: Another
scripting language,
found mainly on Microsoft
Servers) |
|
| .ASPX |
| (.net
technology: Microsoft's
latest scripting ability
and more, will be
found on Microsoft
Servers running the
.net technology) |
|
| .CGI |
| (Common
Gateway Interface:
Calls a computer program
for caluculations
or processing, computer
program can be a wide
variety of languages) |
|
| .PL |
| (Perl
Extension: Calls a
Perl Script for processing) |
|
| So
every time you see
a web page with a
different extension
other than .htm
or .html
you know more is going
on. |
|
| What
is CGI? Perl? |
| CGI
(Common Gateway Interface)
is a very common word
when web hosting is
mentioned. Frequently,
but incorrectly, people
usually asked web
hosting providers
if they can run CGI
scripts on their accounts.
What they are actually
asking, albeit indirectly,
is if they can use
CGI to run computer
programs on their
website. |
|
| CGI,
in simple terms, is
essentially an intermediary
between the a computer
script and the web
site. It operates
to take the information
from the web page
and pass it to a computer
script (program) and
do whatever the computer
program says to do.
CGI is not a computer
language per se, but
a common language
for different computer
programs to interact
with the web pages
(hence Common Gateway
Interface). |
|
| One
of the recognized,
and highly used, computer
program languages
which uses CGI is
Perl. Perl is a high
level computer language
which can manipulate
files, text and perform
system operations
with ease. Perl scripts
are highly used on
the web and quite
frequently you hear
about a very common
perl script known
as "formmail."
A formmail script
is essentially a computer
program written in
Perl which takes information
from a web page and
e-mails the information
to someone. This is
accomplished when
someone fills out
a form on a web page
and presses a button.
The button then starts
the computer program
(formmail) which uses
CGI to get the information
from the webpage and
e-mails the information.
Perl scripts have
been written to do
quite a lot of things
on a web site and
it is a very powerful
language. But, it
is not the only computer
language which can
interact with a web
page. Some others
are ASP, PHP, C, Python,
etc. |
|
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