For whatever reason, you may need to knwo the absolute path name, in osCommerce this is referred to as the FS_CATALOG etc... to find this out is easy!

Open up a program like Notepad, and add this code to it

<?php
echo $_SERVER["DOCUMENT_ROOT"]
?>

save the file as ab.php upload it to your site and call it in our browser, ie
http://www.yoursite.com/ab.php it will then produce the server document root, it depends on the server but usually looks like /home/username/public_html/

easy!