65HOST – the Acorn’s BBC emulator.
It was originally given away with the Acorn Axxxx series computers and called “Archimedes”. Although later models dropped this name, it is still copyrighted (and currently owned by Pace Microtechnology Limited), so if you haven’t got a copy then it may now be difficult to get hold of one legally. It isn’t now given away with modern RISC OS machines.
However, assuming you have a copy that perhaps you got with an older Acorn machine and kept when you upgraded then you might wish to make use of it. It emulates a BBC B but with ADFS rather than the DFS you might expect. It will allow direct access to floppy discs, CDs (if your computer has a CD-ROM drive fitted) and also your computer’s Hard Drive. It follows the Acorn numbering standards, so if you copy an entire floppy disc onto your Hard Drive and then run it from within !65Host, you need to change any references to drives 0, 1, 2 and 3 within the files. Otherwise, the program will start accessing the floppy drive.