About Universal Resource Locators (URLs)

To understand how a single page is kept distinct in a world of electronic pages, you ought to recognize its URL, short for Uniform Resource Locator. Every page has a unique URL just like every person has a unique palm print. (Arguments persist as to which is more cryptic.)

A URL is text used for identifying and addressing an item in a computer network. In short, a URL provides location information and browsers display URLs in a Location field. Most often you don't need to know a page's URL because the location information is built into a highlighted link; browsers already have the URL available when you click on highlighted text, press an arrow button, or select a menu item. But sometimes you won't have an automatic link and instead have only the text of the URL (perhaps from a friend or a newspaper article). The browser gives you the opportunity to type in a URL directly into the Location text field or the URL dialog box produced by the Open... menu item from the File menu, depending on which browser you use. Using the URL, the browser will bring you the specified page just as if you had clicked on an automatic link.

Here's a sample URL: http://www.science.uva.nl/research/

Browsers use the URL text to find a particular item, such as a page, among all the computers connected to the Internet. Within the URL text are components that specify the protocol, server, and pathname of an item. Notice that the protocol is followed by a colon (http:), the server is preceded by two slashes (//www.science.uva.nl), and each segment of the pathname is preceded by a single slash (/research/).

The first component, the protocol, identifies a manner for interpreting computer information. Many Internet pages use HTTP (short for HyperText Transfer Protocol). Other common protocols you might come across include file (also known as ftp, short for File Transfer Protocol), news (the protocol used by Usenet news groups), and gopher (an alternative transfer protocol).

The second component, the server, identifies the computer system that stores the information you seek. Each server on the Internet has a unique address name whose text refers to the organization maintaining the server. The IP number may also be used.

The last component, the pathname, identifies the location of an item on the server. For example, a pathname might identify a page by specifying the name of the file comprising the page (such as /welcome.html) as well as the name of one or more folders that store a file (/home).

When a URL is specified without a specific filename, our FNWI daemon configuration will first attempt to access a document in that directory named index.html. If that file does not exist, the server will produce a list of files in the directory. When present, the list is preceded by the file HEADER, and followed by the README. These two files will not be listed `as file'.