Xref:	news2.mv.net comp.os.msdos.djgpp:2924
From:	u7711501 AT bicmos DOT ee DOT nctu DOT edu DOT tw (Jih-Shin Ho)
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Detecting drives
Date:	22 Apr 1996 04:22:11 GMT
Organization:	Computer Center, National Chiao-Tung University, Taiwan
Lines:	34
Message-ID:	<4lf1hj$mhm@ccnews.nctu.edu.tw>
References:	<Pine DOT SUN DOT 3 DOT 91 DOT 960416204807 DOT 6630K-100000 AT is>
NNTP-Posting-Host:	bicmos.ee.nctu.edu.tw
NNTP-Posting-User:	u7711501
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

Eli Zaretskii (eliz AT is DOT elta DOT co DOT il) wrote:
: 
: On 15 Apr 1996, Jih-Shin Ho wrote:
: 
: > The above code can detect all drives that DOS understands. For example,
: > network drive.
: 
: Not so fast.  "Network drives" might mean Novell 3.x, and you'd be 
: surprised to see what you can get there, since Novell 3.x hooks Int 21h 
: before DOS and thus any info about Novell drives bypasses DOS entirely.

If DOS doesn't understand this drive, how can it use the drive ?
For example, 'dir x:'

: 
: > 0x4409 DOS function call doesn't touch disk drive. It uses (I am not sure) the
: > internal data structure in DOS kernel for the detection.
: 
: This might be a source of another problem, this time with CD-ROMs.  You
: could get successfull return from 4409 with stale data even if there is no
: disk in the drive.  That's because no DOS filesystem exists on the CD,
: it's an illusion created entirely by MSCDEX.  Try putting a disk into a CD
: drive, make some DOS call, then remove the disk, close the door and issue
: 4409.  I've seen similar functions returning ``valid'' data about a disk
: that's long ago gone in such cases (but I didn't try this with 4409, so I
: can't say for sure). 

But the title is 'detecting drive', not 'detecting valid disk in drive'.
4409 only tells you which drive is valid, it can't tell if there is a
disk in drive.

-- 
  Jih-Shin Ho, National Chiao Tung University
  u7711501 AT bicmos DOT ee DOT nctu DOT edu DOT tw

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