What do these codes mean?

If you're not used to the Internet, and perhaps even if you are, you may be wondering what the codes mean that you see after descriptions of pages on the World Wide Web or other resources.

Let's look at an example:

	http://www.herald.co.uk/index.html

The code as a whole is called a URL; Universal Resource Locator. The idea is to provide a standard format for describing the whereabouts of any resource available via the Internet.

This code has three important parts.

http:

This tells the reader how to access the resource. HTTP stands for HyperText Transfer Protocol, which means that you should use a World Wide Web browser such as Mosaic, Netscape or Lynx to read it. Other alternatives might be ftp:, standing for File Transfer Protocol, used to retrieve files to your machine for later use, or telnet:, which means that you would actually log into the other machine. (http: and ftp: don't require actual logins, just retrieval of files which may or may not be viewed then and there.)

www.herald.co.uk

This specifies which of the millions of machines with access to the Internet actually holds the resource. It will refer to one specific machine (in this case it's the Herald Information Systems main server). Two or more names may refer to the same machine; for instance, at present, ftp.herald.co.uk and www.herald.co.uk are the same machine, but in the future this could change. Using the name of a machine means that such changes will not affect anyone wishing to use the resource.

index.html

This tells you the name of the resource on that machine. The part of the name after the dot tells your system that the file is written in HyperText Markup Language - in other words, it is a page for the World Wide Web. Other extensions include .gif, which indicates a graphics file in a particular format, and .zip. which shows a file which has been compressed to take up less disk space.

This part of the URL need not be as simple; for instance

http://newtoo.manifest.com/WhatsNewToo/index.html

shows that the resource you want should be accessed through the World Wide Web, is held on the machine newtoo.manifest.com, but the actual file is held in a subdirectory called WhatsNewToo.

URLs may look complicated, but they are very useful if you need to specify exactly what someone should look for, what they should use to find it and whereabouts they should be looking.