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- 6502Em: The Filing System
- =========================
-
- The emulator provides a full filing system by means of the
- VDFS ROM.
- The following commands can be used to select the Virtual DFS
- ROM as the current filing system:
-
- *DISC
- *DISC
- *ADFS
- *FADFS
-
- In addition, the following commands are offered:
-
- *Quit (Return to the desktop)
- *Desktop (Return to the desktop)
- *Shadow (dummy command)
- *SRLoad (load image into sideways RAM)
- *SRWrite (copy memory into sideways RAM)
-
- Partial emulation of OSWORD &72 and &7F is performed
- (reading only!)
- This allows certain disc protection schemes to work.
-
-
- The DFS filing system structure is fully emulated
- by noticing when an ADFS directory's name is one
- letter long.
-
- eg if your Currently Selected Directory (CSD)
- is ADFS::HD.$.BBC.Games.J then:
-
- *DIR K will attempt to set the CSD to ADFS::HD.$.BBC.Games.K
-
- *DIR J will leave the CSD unaltered
-
- *DIR $ will set the CSD to ADFS::HD.$.BBC.Games
- (to change to the "real" root directory, use *DIR :4.$)
-
- *DIR ^ will set the CSD to ADFS::HD.$.BBC.Games
-
- eg if your CSD is ADFS::HD.$.BBC.Games then:
-
- *DIR $ will leave the CSD unchanged
-
- *DIR ^ will set the CSD to ADFS::HD.$.BBC
-
- *************************************************************
- * If your CSD is set to ADFS::HD.$.BBC.G.L then ambiguity *
- * can arise, so single letter directories should NOT be *
- * used within each other. *
- *************************************************************
-
- Drive numbers within filenames (eg :0.E.Jameson) are ignored
- so that you can save positions of games onto your hard disc.
- To specify a drive, use ADFS::0.Jameson
-
- *Drive and *Mount are ignored
- To change drive use *DIR :0, *DIR ADFS::0, *DIR ADFS::HD etc
-
- RISC OS's CSD is not changed by the emulator, allowing
- several incarnations of the emulator to be active.
-
- Some filing systems (eg DOSFS) do not support OSGBPB 8,
- so programs that use it will not work on such filing systems.
-
- OSFSC, OSFIND, OSGBPB, OSBPUT, OSBGET, OSARGS, OSFILE
- are all fully supported.
-
- In addition, OSGBPB 9 is partially supported (for the
- current directory):
-
- block?0=number of files to read (number of files read)
- block!1=address in memory of data
- block!5=length of data block
- block!9=sequential pointer (0 for first call, -1 when finished)
-
- RISC OS errors are passed back into the emulator via BRK.
-
- Filing system operations appear instantaneous to the emulator
- (ie do not run filing system benchmarks within the emulator!)
-
- Although the operating system normally appears to be ROM,
- it can be overwritten by filing system calls (eg *Load)
-
- Files that will extend beyond &FFFF will generate an error
- if you try to load them.
- (normally files might wrap round back to &0000)
-