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From: Ralf.Brown@B.GP.CS.CMU.EDU
Newsgroups: comp.os.msdos.programmer
Subject: Re: Abort, Retry, Fail (Summary)
Message-ID: <28104b45@ralf>
Date: 20 Apr 91 14:08:05 GMT
Sender: netnews@cs.cmu.edu (USENET News Group Software)
Organization: Carnegie Mellon University School of Computer Science
Lines: 40
In-Reply-To: <1991Apr19.131352.255@aplcen.apl.jhu.edu>

In article <1991Apr19.131352.255@aplcen.apl.jhu.edu>, tcs@mailer.jhuapl.edu (Carl Schelin) wrote:
}As a final bit of information, here are the values returned by dx when you 
}generate int 21 with AX = 0x4409:
}
}               VDISK     = 0x0800
}               BERNOULLI = 0x0802
}               LOCAL     = 0x0840
}               LOCAL     = 0x0842      /* for Compaq Dos v4.01 */
}               NETWORK   = 0x1756
}               EXTERN    = 0x4840      /* external 3.5" for example */
}               SUBST     = 0x8840
}
}Joined and Assigned drives take the characteristics of the original drive 
}in this case.
}
}I've sent this information to Ralf Brown (INTER291 interrupt list). It may 
}be a correction to his list.

I did a little further digging, and the interrupt list now reads:

INT 21 - DOS 3.1+ - IOCTL - CHECK IF BLOCK DEVICE REMOTE
	AX = 4409h
	BL = drive number (00h = default, 01h = A:, etc)
Return: CF clear if successful
	    DX = device attribute word
		bit 15: drive is SUBSTituted
		bit 12: drive is remote
		bit  9: direct I/O not allowed
	CF set on error
	    AX = error code (01h,0Fh) (see AH=59h)
Note:	on local drives, DX bits not listed above are the attribute word from
	  the device driver header (see AH=52h); for remote drives, the other
	  bits appear to be undefined
SeeAlso: AX=4400h,AX=4408h,AX=440Ah,INT 2F/AX=122Bh

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