Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!iuvax!cica!tut.cis.ohio-state.edu!pt.cs.cmu.edu!b.gp.cs.cmu.edu!ralf
From: ralf@b.gp.cs.cmu.edu (Ralf Brown)
Newsgroups: comp.sys.ibm.pc
Subject: Re: the MS-DOS volume label
Keywords: info
Message-ID: <5419@pt.cs.cmu.edu>
Date: 5 Jul 89 00:01:53 GMT
References: <8002@bsu-cs.bsu.edu> <1676@neoucom.UUCP>
Organization: Carnegie-Mellon University, CS/RI
Lines: 41

In article <1676@neoucom.UUCP> wtm@neoucom.UUCP (Bill Mayhew) writes:
}
}The volume label is just another file name in the root directory
}with one of the attribute bits set to indicate that it is the
}volume ID.
}
}You could read the absolute disk block(s) that comprise the root
}directory and set the name with an assembly program, I suppose.

Not only is that more work, it can be dangerous if used on nonstandard
disks.  DOS calls suffice, as the following excerpt from running "INTERCEP"
on DOS 3.10 "LABEL.COM" shows:

71DC:03EA  2111   Search for first file matching FCB at 71DC:0115
71DC:0573  2113   Delete file using FCB at 71DC:0142
71DC:0585  215b   Create new file (name at 71DC:0103, attr. 08)
71DC:058D  213e   Close file handle #0005

First, we search for the label using the FCB version of FINDFIRST/FINDNEXT,
passing an extended FCB with the attribute mask set to find volume labels.
Since this call will also find normal files, we have to loop until the file
found actually has the volume label bit set.

Next, the existing label is removed by doing a DELETE call using an extended
FCB with the attribute mask set to volume label.

Finally, we create a new file with the volume label attribute (bit 3==08h)
set.  INT 21h/AH=5Bh does not exist under DOS 2.x, so you would have to use
the FCB file creation function.  Since the create opens the file, we have to
close it.

}You might be able to use the DOS function calls of 17H or 56H to
}rename the disk, but I am not optimistic.  I didn't feel like

I believe that these calls will fail.

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