Although many Perl, PHP and other CGI scripts are available as a free download, they need to be installed to your website before they can be used. For example, you have downloaded a free discussion forum script and have discovered the installation instructions contain this thing about file permissions. CHMOD this file to 777 or set file permissions to this other file to 755 and the list goes on. From here you have 2 options. 1. Install the script yourself. 2. Pay someone (usually the developer) to install it. If you want to install your own scripts, you'll need to know how to set file permissions. If file permissions are not set correctly, the script will not work. This easy to use free CHMOD calculator will show you how to set file permissions in both Octal and Symbolic format. It will teach you how to set file permissions until you remember how to do it yourself. No installation is required. Just download the program and double-click to run it.