Xref:	news2.mv.net comp.os.msdos.djgpp:2729
From:	malcolm AT manawatu DOT gen DOT nz (Malcolm Taylor)
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Detecting drives
Date:	Mon, 15 Apr 1996 09:14:57 GMT
Organization:	Grafik Software
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Message-ID:	<4kt7k5$mr3@news.manawatu.gen.nz>
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u7711501 AT bicmos DOT ee DOT nctu DOT edu DOT tw (Jih-Shin Ho) wrote:

>Malcolm Taylor (malcolm AT manawatu DOT gen DOT nz) wrote:
>: Really? Which DPMI providers do this? I use a findfirst on the drive
>: looking for a volume label, which of course fails with no disk in the
>: drive. Would this cause a GP fault on some DPMI providers?
>: 
>This is what I write to detect disk drive (physical and virtual):
>  for (i = 0; i < 26; ++i) {
>    regs.x.ax = 0x4409;      /* get drive flags */
>    regs.h.bl = i + 1;  /* 1-based dos drive */
>    intdos(&regs,&regs);
>    if (!regs.x.cflag) printf("%c ",'A' + i);

Does this catch cd-rom drives, remapped Floppies (ie a floppy drive
that is mapped as B: even though it is A:)?
The question I had was about detecting whether the disk was in the
drive. It seems that some DPMI providers will give GP faults if you
try to use a DOS call on an empty drive (ie to see if it is empty).
The only way of detecting a ready CD-ROM drive that I know of (using
int 0x2f) may also cause a crash.
It seems that reading a sector with the BIOS is the only way to get
around this (on floppies).

Malcolm

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