Robert Bonomi <bon...@mail.r-bonomi.com> wrote: > > MSDOS/PCDOS had no _documented_ functions to directly access the > > disks, bypassing the file system, but the functions _did_ exist. > > I'm sure you can provide the DOS 'function number' for those calls, > and cites to published data confirming.
They may have involved a dedicated INT or two, e.g. INT 25H and/or INT 26H, rather than INT 21H with a function number in AX. I could have provided specifics 25 years ago :) when I was involved with this stuff on a daily basis. I have no idea whether it was ever published, but it was well known to those of us who were using it in system-level utilities. > > The debugger's "read sector" and "write sector" commands used them, > > and I suspect chkdsk, scandisk, and format probably also used them > > although I never had occasion to verify one way or the other. > > My experince in porting MSDOS 3.1 to a non pc-clone architecture was > that fdisk, format, chkdsk, debug, and sys all invoked INT 13H directly. I've got you beat in seniority :) I was mostly working on 2.x, and got out of the business somewhere around 3.1 or 3.2. I think I'd remember if our stuff had quit working when 3.x came along, but it's possible that those interfaces were only retained for compatibility -- to avoid breaking old 3rd-party code -- and that the MS userland had been revised to call the BIOS directly (since by then the market consisted almost entirely of PCs and clones -- decidedly not the case in the 2.0-2.1 timeframe). BTW fdisk _would_ always have had to use BIOS calls, or some other platform-specific mechanism, since the direct disk access in DOS was restricted to the DOS partition(s). The parameters were something like buffer address, logical drive number (0 => A:, 2 => C:, etc.), starting sector within the logical drive, and number of sectors. _______________________________________________ firstname.lastname@example.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "freebsd-questions-unsubscr...@freebsd.org"