You can create them in Notepad or any other Text Editor on a Windows PC or with 'vi' on the SCO Box. If you create them for the 8700 (SCO) version of Micros using a PC editor, make sure to convert the file, using something like DOS2UNIX to remove the CRLF at the end of each line. Also, FTP them to SCO in Binary Mode.
The syntax of an ISL file is very much like BASIC, and offers several additional properties, methods, and events that are specific to the Micros POS. You can get the SIM manual on most Micros installation CD's.
Once you have created the file, you would need to install (copy or ftp) it to the etc directory in order for the POS to see it. Then, you add a reference to the ISL (SIM) in the Interfaces section of the Configurator, Add the Additional reference for each Revenue Center, and begin adding TouchScreen keys to call the SIM inquiry events.
Hope this helps...