UCSD P-system could only allocate contiguous disk space. So a disk that had become "checkerboarded" by writing and deletng files had to be defragmented, using a spplied utility called "Crunch". Was that adequately protected against catastrophes caused by interruption? Softech and UCSD Regents filed trademark registration for "XenoFile", and listed it as a product, but as near as I can tell, NEVER sent out any copies. (February 1987, I went to the Patent and Trademark Office outside of Washington, Dc, and researched some trademarks, in preparation for my trademark registration) They also announced a "universal disk format" for ALL machines, but never had a clue about how to do anything compatible with FM, MFM, and GCR.