On Fri, 21 Apr 2000, Fred Cisin (XenoSoft) wrote:
> On Fri, 21 Apr 2000, Don Maslin wrote:
> > > what the CP/M-86 would see on the MS-DOS format.
> > It gives you a big fat error message.
>
> In THIS case, due to sector size differences. But not ALWAYS. I have
> seen non-CP/M disks with E5 where a CP/M directory would have been.
>
> MS-DOS will give a big FAT :-) error message when trying to read CP/M
> (actually "Probable Non-DOS disk") because it is picky about what it
> expects to see in the F.A.T.
>
> Due to reserved tracks, on 8" double density, CP/M's DIRectory will
> fall AFTER the end of the MS-DOS directory, where the first file would
> otherwise be likely to be. You're right that that would almost certainly
> be content that would choke CP/M. But with very short files and large
> clusters, and with sector interleave, it is entirely possible to have CP/M
> looking at unused sectors.
>
> Both MS-DOS and CP/M will accept and assume "empty" when encountering
> a DIRectory (not the MS-DOS F.A.T.) sector of all E5. MOST MS-DOS formats
> fill the empty directory sectors with 00, but not all. Some use E5, some
> F6 with E5 every 32 bytes, ... What would CP/M-86 report for a directory
> sector of all 00? An MS-DOS format with a large directory could easily
> leave the END of the MS-DOS directory sectors where the first of the CP/M
> directory sectors would be.
CP/M-80 displays the full directory except that the "00"s are displayed
as ":"s. I zeroed out the first 512 byte sector of a CP/M-80 directory
and it displayed 16 colons followed by the actual file names in the
remaining sectors. I would assume that CP/M-86 would do the same, and
it does.
- don
> I don't often see use of USER in CP/M disks. Sometimes, but not often. I
> think that it is more likely that they gave Sellam blank formatted
> diskettes.
>
> --
> Fred Cisin cisin_at_xenosoft.com
> XenoSoft http://www.xenosoft.com
> 2210 Sixth St. (510) 644-9366
> Berkeley, CA 94710-2219
>
>
Received on Sat Apr 22 2000 - 16:47:56 BST