URL Addresses (primer)

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URL Addresses

A Uniform Resource Locator or URL address is a wedding of the information in the IP address for a machine and the information in its local file structure. Thus a URL address gives the location of a file, not with respect to a single computer, but with respect to the entire Internet!
What Are URLs: An Analogy

Imagine that you live in a large building and that your address in the building corresponds to a room number. We might call that a local address: anyone in the local building can locate you by using your room number. That is analogous to the name of a file on a single computer: anyone logged into that computer can locate a file on the computer if they know its name, and what folders or directories it resides in (and have permission to look in those directories).
Now imagine that someone from another country wants to locate you. The local address within the building is no longer sufficient because it doesn't specify how to find your building. At the very least, it is necessary to specify additional information giving the country, city, street, and so on of the building in which you reside.
This is now analogous to the information that a URL address provides: a URL address gives a unique address for a file with respect to anywhere on the Internet, just as your complete residential address gives a unique way to locate you from anywhere in the world. Thus, URL addresses allow the computers of the Internet to behave at a certain level as if they were a single computer.
What do URL Addresses Look Like?

Here is an example of a URL address:

http://csep10.phys.utk.edu/webcourse/browser/textfile.html
This is a functioning URL address, and it is also a hypertext link (notice the color and the underline, and that if you hold the mouse over the link the pointer turns into a pointing hand, all of which indicate that this is a link). Therefore, you can go to it by clicking on it. Try it (but then come back here, by using the Back button on the browser).

URL's Can Address More Interesting Things

The preceding example shows the use of a URL to specify a file containing text. However, URL's can be used to address much more general things. For example, try the following links corresponding to
An image at http://csep10.phys.utk.edu/webcourse/browser/usa2.gif
A sound file at http://csep10.phys.utk.edu/webcourse/browser/hasta_la_vista.au
A movie file at http://csep10.phys.utk.edu/webcourse/browser/goldgate.mpg
Therefore, we see that a URL address is a very powerful thing, allowing us to address many different kinds of files.


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		URL Addresses A Uniform Resource Locator or URL address is a wedding of the information in the IP address for a machine and the information in its local file structure. Thus a URL address gives the location of a file, not with respect to a single computer, but with respect to the entire Internet! What Are URLs: An Analogy Imagine that you live in a large building and that your address in the building corresponds to a room number. We might call that a local address: anyone in the local building can locate you by using your room number. That is analogous to the name of a file on a single computer: anyone logged into that computer can locate a file on the computer if they know its name, and what folders or directories it resides in (and have permission to look in those directories). Now imagine that someone from another country wants to locate you. The local address within the building is no longer sufficient because it doesn't specify how to find your building. At the very least, it is necessary to specify additional information giving the country, city, street, and so on of the building in which you reside. This is now analogous to the information that a URL address provides: a URL address gives a unique address for a file with respect to anywhere on the Internet, just as your complete residential address gives a unique way to locate you from anywhere in the world. Thus, URL addresses allow the computers of the Internet to behave at a certain level as if they were a single computer. What do URL Addresses Look Like? Here is an example of a URL address: http://csep10.phys.utk.edu/webcourse/browser/textfile.html This is a functioning URL address, and it is also a hypertext link (notice the color and the underline, and that if you hold the mouse over the link the pointer turns into a pointing hand, all of which indicate that this is a link). Therefore, you can go to it by clicking on it. Try it (but then come back here, by using the Back button on the browser). URL's Can Address More Interesting Things The preceding example shows the use of a URL to specify a file containing text. However, URL's can be used to address much more general things. For example, try the following links corresponding to An image at http://csep10.phys.utk.edu/webcourse/browser/usa2.gif A sound file at http://csep10.phys.utk.edu/webcourse/browser/hasta_la_vista.au A movie file at http://csep10.phys.utk.edu/webcourse/browser/goldgate.mpg Therefore, we see that a URL address is a very powerful thing, allowing us to address many different kinds of files.