Under most circumstances, when an MFS has finished, it calls the next filing system, passing it all arguments, including those that have been modified. The next filing system operates on those arguments as if they had come directly from BASIC+.
The next filing system may be the BFS, or it might be an additional MFS. If there is another MFS installed on the file, the current MFS calls the next MFS. If there are no more MFSs for the file, the MFS calls the BFS directly.
