Understanding URL's
(Uniform Resource Locators)

A URL is the address of a web page. URL’s are unique to each page they represent, just like street addresses are unique to each building they represent. They consist of a specific set of information that directs the computer where to look for a web site. As you supply more information, the computer will take you to more specific areas of the web site. You will always see a URL in the location or address bar of your web browser. You can enter URL’s in this area as well.

Let’s examine a URL:

http://www.carnegielibrary.org/locations/pccenter/helpsheets/urls.html

http is the protocol. Http stands for hypertext transfer protocol. Another protocol is ftp, which stands for file transfer protocol. These protocols tell the computer what action to take and coordinate the transfer of information from one computer to another. In most cases, you no longer need to enter http in the location bar when typing in a URL.

www is the service to be used on the Internet. It is usually www although it can be other things like "mail".

carnegielibrary is the domain name. This is the name of the company or server that houses this site. In this case, it is clpgh standing for Carnegie Library of Pittsburgh.

.org is the domain suffix. It helps identify what type of site you are viewing, commercial or otherwise. There are a limited number of domain suffixes and each signifies a different type of site.

• .com represents business, commercial, and personal web sites. Examples of .com’s include www.honda.com or www.potterybarn.com.



• .edu Used by higher educational institutions, like technical schools, colleges, and universities. Examples include Pitt’s address at www.pitt.edu and Penn State’s address at www.psu.edu.



• .net used by networked organizations or internet service providers like www.webtv.net.



• .org organizations that are usually non-profit. Our address, www.clpgh.org, is one example of this type of site.



• .mil used by the military.



• .gov denotes governments agencies. Examples are www.whitehouse.gov and www.cia.gov

/locations/pccenter/helpsheets/ these are folders. You could type www.carnegielibrary.org in the "Location" or "Address" bar, but this would take you to the Carnegie Library of Pittsburgh main page. By typing in these two folder names you specify the exact location of where you want to go. In this case, first to library’s web site, and then to the PC Center site. Other folders in the library are /locations/reference/ for the Reference Services web site or /locations/pennsylvania/ for the Pennsylvania Department web site.

url.htm this is a file name. Usually, files are the equivalent of a web page or, in other words, one page of a book. Typing in all the information up to this point would take you to the Carnegie Library of Pittsburgh, PC Center. Once you add the helpsheet folder name and the file name you get taken to specific page within the PC Center web site, in this example, this page. The .htm or .html is the file extension. It tells the computer how to interpret the information contained in the file. .htm and .html tells the computer that this is a HTML or Hypertext Mark-up Language file. HTML is simply the computer language responsible for web pages.

Now you’re ready for a quick analogy!

All houses need four things to be houses, a roof, a floor, walls, and an entry point. URL’s also need four things to work, a protocol, a service, a domain name, and a domain name suffix. Other items, like windows, plumbing, and electric increase a home’s effectiveness but they are not necessary. Just like these other items, the folders and file name will increase a URL’s effectiveness but you do not need them to use a URL.

Take A Minute...

Next time you are reading a magazine or a newspaper take a minute and look at some ads. My bet is you'll see some URL's only now you'll know what they mean!

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