Content deleted Content added
→8-bit usage: At least the Electron and the Master Compact were primarily used with 3.5" floppies. |
PaulBoddie (talk | contribs) →8-bit usage: Removed "citation needed" for ZYSYSHELP remarks since they are supported by the existing source. |
||
| (2 intermediate revisions by 2 users not shown) | |||
Line 1:
{{
{{infobox filesystem
|name = ADFS
Line 26:
|OS = [[Acorn MOS]], [[RISC OS]]
}}
The '''Advanced Disc Filing System''' ('''ADFS''') is a computing [[file system]] unique to the [[Acorn Computers Ltd|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 disc]]s was added (using a [[Western Digital FD1771|WD1770 floppy disc controller]]) and on later [[32-bit]] systems a variant of a PC-style floppy controller.<ref>{{ cite book | url=http://chrisacorns.computinghistory.org.uk/docs/Acorn/Manuals/Acorn_ADFSUG.pdf
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 (printed circuit board)|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 <code>$</code> now indicated the hierarchical root of the filesystem. <code>^</code> was used to refer to the parent directory, <code>@</code> the current directory, and <code>\</code> was the previously visited directory.
Line 35:
ADFS on 8-bit systems required a WD1770 or later 1772-series floppy controller, owing to the inability of the original Intel 8271 chip to cope with the double-density format ADFS required. ADFS could however be used to support hard discs without a 1770 controller present; in development the use of hard discs was the primary goal, extension to handle floppies came later.{{citation needed|date=March 2021}} The 1770 floppy controller was directly incorporated into the design of the Master Series and B+ models,<ref name="acornuser198507">{{ cite news | url=https://archive.org/details/AcornUser036-Jul85/page/n161/mode/2up | title=B+ Grading | work=Acorn User | date=July 1985 | access-date=18 October 2020 | last1=Smith | first1=Bruce | pages=160–161 }}</ref> and was available as an upgrade board for the earlier Model B.<ref name="1770_disc_interface">{{ cite book | url=http://chrisacorns.computinghistory.org.uk/docs/Acorn/Misc/Acorn_1770DiscIF.pdf | title=1770 Disc Interface | publisher=Acorn Computers Limited | access-date=6 March 2021 }}</ref><ref name="1770_disc_upgrade_kit">{{ cite book | title=1770 Disc Interface Upgrade Kit Fitting Instructions | url=http://chrisacorns.computinghistory.org.uk/docs/Acorn/Tech/Acorn_1770DiscIFUpgradeKit.pdf | publisher=Acorn Computers Limited | date=August 1985 | issue=1 | access-date=11 March 2021 }}</ref> ADFS could be added to Model B and B+ systems with an additional upgrade.<ref name="adfs_upgrade">{{ cite book | url=http://chrisacorns.computinghistory.org.uk/docs/Acorn/Misc/Acorn_ADFSUpgrade.pdf | title=ADFS upgrade | publisher=Acorn Computers Limited | access-date=6 March 2021 }}</ref>
The [[Acorn Electron#Acorn Plus 3|Acorn Plus 3]], Acorn's official disc expansion for the Acorn Electron, was supplied with ADFS as standard, but this implementation featured various notable bugs. A file called {{mono|ZYSYSHELP}} was "required by the system" and created during formatting.<ref name="plus3ug">{{ cite book | url=http://chrisacorns.computinghistory.org.uk/docs/Acorn/Manuals/Acorn_Plus3UG.pdf | title=The Electron Plus 3 User Guide | publisher=Acorn Computers Limited | date=October 1984 | issue=1 | access-date=6 March 2021 }}</ref>{{rp|pages=7}} This was a kludge. Acorn's original ADFS implementation on the Electron was unreliable when writing to the first few tracks of a floppy disc, so this was a "fix" and simply involved writing a file full of garbage to the suspect part. The ADFS would then skip it.
On the Electron, disc formatting was done via the {{kbd|*EFORM}} command instead of the established {{kbd|*FORM40}}/{{kbd|*FORM80}} DFS commands. Note additionally that the {{kbd|*EFORM}} command differs from the equivalent {{kbd|*AFORM}} command for the 1770 ADFS on the BBC Microcomputer. This is possibly as a result of needing to create the {{mono|ZYSYSHELP}} file on the Electron. The {{kbd|*EFORM}} command was only supplied on the Welcome disc that was shipped with the Plus3, and was not included in the ROM.<ref name="plus3ug" />{{rp|pages=48}}
| |||