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Relative Addresses
Let's use your homepage folder and files to illustrate the difference
between absolute and relative URL addresses. Open your homepage
folder and do the following:
- Create a new folder inside your homepage folder; call
it "gifs".
- Use the Browser to go to the address
http://www.alco.org/help/web_page/next.gif
Save the image that is displayed into your
homepage folder with the default name "next.gif" by
holding the right mouse button down over the image, choosing
"Save Picture as", and selecting your homepage folder in the
resulting dialog box.
- Use the Browser to go to the address
http://www.alco.org/help/web_page/previous.gif
Save the image that is displayed in the folder "gifs" that
you created inside your homepage folder with the default
name "previous.gif" (NOTE: read the instructions carefully;
this file goes to a different folder than the one in the previous
step!).
- Open your homepage file index.html with the editor
and insert the following HTML code at a convenient place:
<h2> Examples of Absolute and
Relative URL's </h2>
This image has an absolute address
of "?":
<p>
<img src="?">
<p>
This is the same image displayed
with a relative address "next.gif":
<p>
<img src="next.gif">
<p>
Here is another image in a subdirectory
"gifs" of the present directory; it is
displayed using the relative address
"gifs/previous.gif"
<p>
<img src="gifs/previous.gif">
<p>
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Save the homepage file, but leave the file open in the editor.
- Use "Open" from under the "File" menu of your Web
Browser to open the image "next.gif" saved in your homepage
folder. Copy the address displayed in the "Address:" window of
the browser with the mouse. This is the (absolute) URL
address of the file on your machine. It will typically look something
like:
file://c:/myfolder/next.gif
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(but the exact directory path will depend on your machine).
Go to the homepage file still open in the editor and
THE TWO OCCURRENCES OF THE QUESTION MARK ()
WITH THE URL ADDRESS YOU HAVE JUST COPIED WITH YOUR MOUSE.
Save the homepage file, and close the editor.
Supplementary Note: The preceding URL is the form
for a URL address of a file on the same machine as the browser.
The "file://" part tells us that. There then follows the absolute
address of the file on the machine. In the example given above
this is c:\myfolder\next.gif, which is the sort of
address you might see on a PC. On a Unix
or Macintosh computer, where
the disks are generally designated by names rather than letters,
you might have a URL such as file:///maindisk/myfolder/next.gif,
where the file has an absolute address of /maindisk/myfolder/next.gif.
Now display your homepage with the browser (reload if necessary).
Your browser display should show something similar to the following:
Examples of Absolute and Relative URL's
This image has an absolute address of "file://c:/help/next.gif":
This is the same image displayed with a relative address
"next.gif":
Here is another image in a subdirectory "gifs" of the present
directory; it is displayed using the relative address "gifs/previous.gif"
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These elementary examples illustrate the difference between absolute
and relative addressing, and how to implement relative addressing
for the two simple (but common) cases where the file being addressed
is either in the same directory as the HTML
file (the next.gif example), or in an immediate subdirectory
of the HTML file (the gifs/previous.gif example). As we
have noted above, it is generally advisable to use relative addressing
in your Web pages to increase portability.
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LaPorte County
301 E. Eighth St. #101
Michigan City, IN 46360
Phone:
219-861-0940
Fax: 219-861-0942
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