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' (Netscape).

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 either of:

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 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 specified).

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