Acorn System Disk File System / Atom DOS
Discs for the System series have an identical catalogue format to those for the BBC Micro, except all entries are in a directory " " (space), disks do not have a cycle number, and files do not have bits 16 and 17 of load and execution addresses.
The places they would occupy are reserved and must be cleared. A BASIC program named DCONV, on the Utility disc, performs this task.
The disk layout is identical to Acorn DFS with some differences shown below:
|Byte||Track 0 Sector 0||Track 0 Sector 1|
|0||First 8 characters of volume title padded with NULs or spaces||Last 4 characters of volume title padded with NULs or spaces|
|5||Number of files|
|7||7||Sectors in volume||0|
|8||File name padded with spaces||7||Load address||0||Last file|
|14||Reserved||17 16||Reserved||9 8|
|15||Lk.||Ascii Space (0x20, 32)||7||Start sector||0|
Differences between Acorn DFS and System DFS
- The Reserved entries must be clear.
- The disk type in bits 2 and 3 of sector 1 byte 6 must be clear as with DFS.
- Lk. in byte 7 is the same as for Acorn DFS
This section is based loosely on the following:
- Acorn DFS disk format - beebwiki.mdfs.net
- Acorn, Watford, Solidisk and Duggan DFS Filesystem Structure mdfs.net