 | This article is written like a manual or guide. (August 2018) |
| Developer(s) | Hugo Tyson, Nick Reeves (Acorn Computers) |
|---|---|
| Full name | Advanced Disc Filing System |
| Introduced | 1983 with Acorn MOS |
| Partition IDs | Hugo or Nick (Directory header/footer) |
| Structures | |
| Directory contents | Hierarchical fixed-length tables |
| File allocation | One range per file plus table of free-space ranges (L), bitmap with embedded file IDs (E) |
| Bad blocks | none (L),[1] marked in bitmap (E) |
| Limits | |
| Max volume size | 512 MB |
| Max file size | 512 MB |
| Max no. of files | 47 per directory (L), 77 per directory (E) |
| Max filename length | 10 characters |
| Allowed filename characters | ASCII (Acorn MOS), ISO 8859-1 (RISC OS) |
| Features | |
| Dates recorded | Modification |
| Date range | 1 January 1900 - 3 June 2248 |
| Date resolution | 10 ms |
| Forks | no |
| Attributes | Load address, execute address and file cycle number (Acorn MOS); File type and modification time (RISC OS); User read/write/execute-only; public read/write/execute-only; Deletion lock |
| File system permissions | None |
| Transparent compression | No |
| Transparent encryption | No |
| Data deduplication | No |
| Other | |
| Supported operating systems | Acorn MOS, RISC OS |
The Advanced Disc Filing System (ADFS) is a computing file system unique to the Acorn computer range and RISC OS-based successors. Initially based on the rare Acorn Winchester Filing System, it was renamed to the Advanced Disc Filing System when support for floppy discs was added (using a WD1770 floppy disc controller) and on later 32-bit systems a variant of a PC-style floppy controller.[2]
Acorn's original Disc Filing System was limited to 31 files per disk surface, 7 characters per file name and a single character for directory names, a format inherited from the earlier Atom and System 3–5 Eurocard computers. To overcome some of these restrictions Acorn developed ADFS. The most dramatic change was the introduction of a hierarchical directory structure. The filename length increased from 7 to 10 letters and the number of files in a directory expanded to 47. It retained some superficial attributes from DFS; the directory separator continued to be a dot and $ now indicated the hierarchical root of the filesystem. ^ was used to refer to the parent directory, @ the current directory, and \ was the previously visited directory.
The BBC Master Compact contained ADFS version 2.0, which provided the addition of format, verify and backup commands in ROM, but omitted support for hard discs.[3]
- ^ Cite error: The named reference
reeves-efmtwas invoked but never defined (see the help page). - ^ Advanced Disc Filing System: User Guide (PDF). Acorn Computers Limited. September 1985. Retrieved 1 August 2016.
- ^ "Taking the lid off the Master Compact". Acorn User. October 1986. p. 17. Retrieved 5 September 2020.
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