DISK I/O
Get the process default folder
Are you talking about the folder where the _application_ resides? It's my understanding that this folder becomes the process's default folder when the app is launched, and remains the default folder unless the app explicitly sets a different folder to be the default.
That being the case, you shouldn't need to look at AE stuff. If you get the identity of the default folder shortly after the program starts (before you do any commands which might reset the default), that should be sufficient. You can get a working directory ref. num. for it with the FOLDER function, using the syntax, FOLDER("",0); or you can use FN GETCATINFO, setting the input parameters as follows:
pb.ioNamePtr& = @foldername$ 'to receive the name
pb.ioVRefNum% = 0
pb.ioDirID& = 0
pb.ioFDirIndex% = -1
Rick