Every document has a URL or Uniform Resource Locator. This is jargon for
the document's exact location or address. An example of a URL is:
It is the URL for this document and is displayed within the browser
in the white box next to the label 'Document URL' (Mosaic) or 'Location'
A URL can be broken down into FOUR substituent parts as follows.
1 - Protocol/Facility
The first substituent part specifies the facility. This can be
- http:// (specifically WWW hypertext documents, but may also be text
- ftp:// (FTP archives)
- gopher:// (gopher menus).
2 - Internet Address
This specifies the Internet address. It can be in the form of the
'Domain Name' or 'IP Number' (which we have mentioned earlier in the tutorial).
In our URL example above, the server address we have specified is
3 - Path
The third substituent part is the subdirectory path. Most WWW servers
are based on the UNIX operating system which means that individual
subdirectories are separated by a forward slash ( / ). In our URL example
above, we have specified /education/Internet.
UNIX is case-sensitive therefore the name 'Internet' is NOT equivalent to
the name 'internet'. If the document is in the root directory (ie /) then no
path is specified.
4 - Filename
The final part is the document's filename. This is usually suffixed with
'.html' which specifies that the file format is in WWW hypertext form (more on
this later). ASCII text files are usually suffixed with '.txt' and contain no
hypertext links or images. In the URL example above, the filename specified is
URL.htmland is in WWW hypertext format.
A URL with no filename has had a default filename assigned to it, for
example http://www.cryst.bbk.ac.uk/ specifies the default file which is
the Birkbeck Crystallography Homepage (in other words its Titlepage).
Alternatively, a URL without a file name might be an FTP directory (if the
ftp:// facility was specified) or a Gopher menu (if the gopher:// facility was
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