Question: What is an URL?
Answer: URL (pronounced as in "Duke of ...") is an acronym for Uniform Resource Locator. It indicates the protocol, name and location of a file on a computer network or a local computer.
An URL is different than an e-mail address. An e-mail address is location to send a message file in order to reach a particular addressee. An URL, on the other hand, is a reference to a particular file. If somebody were to ask you for your URL, they would not be asking how to contact you; rather, they would likely be asking for the location and name of your World Wide Web home page file.
An URL is generally made up of three parts. The first part of an URL is the protocol specifier. This is the section of a URL up to an including the first set of slash marks. Examples are "http://" which indicates HyperText Transport Protocol, the standard for World Wide Web files; "ftp://" which indicates File Transfer Protocol, the standard for retrieving a file from a given host; or "file:///" which indicates a computer file of no particular protocol.
The second part of an URL is the domain at which the file resides. This may be an Internet domain such as "www.jrb.com" or it may be a disk drive designation on a local machine or network such as "c|/" or "d|/." The end of a domain section of an URL may also include numbers indicating a network port, such as "www.jrb.com:8181/."
The third part of an URL contains the path to a specific file. For example, the path "images/vacation/italy.html" indicates a file named "italy.html" located in the "vacation" subdirectory of the "images" directory of the server.
It should be noted that an URL will direct a user to a file with a particular protocol, location and name on a particular server computer, but it does not assure a user that the named file at a particular location is the same file that earlier was at the same location. From time to time any file designated by an URL may be altered or replaced by a different file with the same name. Thus, searching for a specific version of a file by using its URL can sometimes be like searching for the perfect wave -- the same location, at the same beach can have different waves from day to day. It's no wonder that it is called surfing.
Additional information regarding URLs can be found at http://www.ncsa.uiuc.edu/demoweb/url-primer.html. Jim Black can be reached at email@example.com; his World Wide Web Page URL is http://www.jrb.com/.
© James R. Black 1997
applet by New Media Marketing Lab at Sun Microsystems, Inc.