I don't know if this has all that you are looking for, but if you open RSLogix and open the Help and select Contents and then the Index tab. Type "Extensions" and you will see a "Files in your project" help topic.
Try that in RSLogix5 and RSLogix500 for descriptions of each format.
Currently I do not have RSLogix and I am not sure if I will be able to get a copy. I am writing a software tool that needs to be able to parse these file formats and I have been unsuccessful in locating the specs for them.