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Phil Gardner's Wrapper.sys & MS-DOS7 bug (Miscellaneous)

posted by Rugxulo(R) Homepage, Usono, 11.12.2009, 07:14

> > I don't intend any continued participation.
> So.

Usually that means "I am too busy to participate fully in every forum out there, esp. since I already attend quite a few". In this case, I think he also means "I'm no longer actively interested in DOS".

> > > In this case, the other DOS variants report a version
> > > of 7.10 to show that they support FAT32.
> >
> > Why on earth would they do that?
> As you explained yourself, there's software that doesn't look for LFN
> functions if the true DOS version isn't at least 7.00. The same
> way, some software wants a true DOS version of at least 7.10.

MS-DOS is by far the most popular DOS. And their version 7 was inside Win95, when LFNs (in VFAT) were first introduced. DR-DOS always tried to one-up them with version numbering (purely for marketing reasons). Of course, MS also most likely used "XBox360" to counter the PS3 (since XBox 2 < PS3 ??).

> > FAT32 is much older.
> So which MS-DOS versions supported it earlier? I read about some "MS-DOS
> 6.23" version, but it apparently wasn't available for retail and I've
> never read someone actually stating they've seen it.

Eh? No, AFAIK, MS-DOS 7.10 means Win95 OSR2 or Win98 or Win98SE, as nothing earlier supported FAT32. (Even DR-DOS only had an unofficial TSR, which I blindly guess was pulled when they discovered MS had patents on it, ugh.)

FreeDOS, as you probably know, by default uses 6.22 as the FAT16 kernel versions and 7.00 (or 7.10, I forget) for FAT32-enabled versions. Maybe ROM-DOS does the same, I dunno. My copy of DR-DOS 7.03 is definitely not LFN aware (except in very few places, e.g. COMMAND.COM), e.g. DR's CHKDSK aborts if any LFNs are found. Of course, DR-DOS reports "IBM DOS 6" to the standard version checks, for compatibility, so you have to go out of your way to test for DR-DOS specifically (int 21h, 4452h "DR").

> > I can imagine that
> > some of them do it to show that they support long file names. They'll
> have
> > surely preferred to indicate it by supporting the int 21h function 71h
> > variants, but no doubt run into software that doesn't look for those
> > variants unless the version number is at least 7.00.
> Yes. Consider that LFN functions even have an explicit installation check
> (21.71A0) which indicates whether LFNs are supported on a particular
> drive. There isn't such an explicit function for FAT32. Therefore it's not
> surprising that software checks the DOS version number for FAT32 support.

Obviously you can use LFNs in any FAT, e.g. FAT12, FAT16, FAT32. Typically Linux calls "msdos" the 8.3 file system and "vfat" the LFN-aware one.

> > I don't give a damn about the other DOSs.
> Yes, I see. But where's the point in talking more about them then?

I'm pretty sure this guy is only interested in modern Windows these days. Also, MS-DOS pretty much clobbered the DOS market. Hence, I blindly guess he's never even tried DR-DOS (and probably doesn't know how good / compatible it is) or others.

> > Moreover, if they
> > want to declare themselves as DOS 7 or higher, then it's their
> > responsibility to get the emulation right. That's the game they play. If
> I
> > have to code specially for them, then they are not perfectly fine DOSs.
> This way (i.e. completely hardcoded offsets) only MS-DOS is your perfectly
> fine DOS. An exact copy of MS-DOS is MS-DOS.

They all have bugs, and if you run into one, you either ignore it, abandon the project (no!), or work around it. Even the hallowed "original" MS-DOS has quite a few annoying quirks and bugs. There are many many patches and rewrites for MS-DOS and Windows to get them to work correctly. (Sadly MS is not too interested in fixing old OSes.) E.g., see my codepage detection patch.

I've actually been (local only) updating my mini distro's disk #3, and a good deal of stuff on there is (funnily enough) for compatibility or bug fixes with other DOS-ish OSes.


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