|
The Advanced Disc Filing System (ADFS) is a computing file system particular 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 (utilising a WD1770 floppy disc controller) and on later 32-bit systems a variant of a PC-style floppy controller.〔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 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. "^" (minus the quotes) was used to refer to the parent 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.〔(User October 1986 - Review - Page 17 )〕 ==8-bit usage== 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 a hard disc without a 1770 controller present. The 1770 floppy controller was directly incorporated into the design of the Master Series and B+ models, and was available as an 'upgrade' board for the earlier Model B. The Acorn Electron's floppy interface (Acorn Plus 3) was an add-on unit, initially available through Acorn and later Pres (aka Advanced Computer Products). The ACP implementation of ADFS fixed a flaw in the Acorn version v1.0, that required the use of a file named ZYSYSHELP. On the Electron, Disk corruption could also occur if attempting to use the *COMPACT command without disabling the blinking cursor. This was due to the fact that the *COMPACT command used screen memory as working space during the operation, and the blinking cursor corrupted that memory space.〔http://www.portices.fr/formation/Res/Info/Dimet/Ordinateurs/AcornBBC/www.stairwaytohell.com/Ressources/r-EU-ACP-E00ADFS.html〕 ADFS supported hard discs, and 3½" floppy discs formatted up to 640 KB capacity using double density MFM encoding (''L'' format; single-sided disks were supported with the ''S'' format (160 KB) and ''M'' format (320 KB)). ADFS as implemented in the BBC microcomputer system (and later RISC OS) never had support for single-density floppies. Hard disc support in ADFS used a modified format, and interfaced to a SCSI-based Winchester unit via the BBC Micro's 1 MHz Bus. Support for IDE/ATAPI style drives has been added 'unofficially' by third parties in recent years.〔(BBC IDE Interface )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Advanced Disc Filing System」の詳細全文を読む スポンサード リンク
|