Path: utzoo!attcan!uunet!lll-winken!lll-ncis!helios.ee.lbl.gov!pasteur!ames!think!ephraim
From: ephraim@think.COM (Ephraim Vishniac)
Newsgroups: comp.sys.mac.programmer
Subject: Re: How does the Finder tell diskettes apart?
Message-ID: <35187@think.UUCP>
Date: 5 Jan 89 21:31:38 GMT
References: <730076@hpcilzb.HP.COM>
Sender: news@think.UUCP
Reply-To: ephraim@think.com (Ephraim Vishniac)
Organization: Thinking Machines Corporation, Cambridge MA, USA
Lines: 22

In article <730076@hpcilzb.HP.COM> tedj@hpcilzb.HP.COM (Ted Johnson) writes:

>I've always wondered how the Finder tells the difference between two
>diskettes which have the same name.  I assume there is some sort of
>unique number associated with each diskette when it is initialized.

>Does anyone know the real story?

Logically, the information has to be somewhere in the volume
information (the stuff in block 2).  The only distinguishing fields I
see are drCrDate (initialization time), drLsBkUp (last modification
time), and the volume name.  My experience is that if you eject a
floppy, modify it on another machine, and re-insert it, it's
considered to be a different floppy.  So, the system certainly uses
drLsBkUp and probably drCrDate as well.

Reference: IM IV-161-166.

Ephraim Vishniac					  ephraim@think.com
Thinking Machines Corporation / 245 First Street / Cambridge, MA 02142-1214

	"He shook his head to clear a momentary system error."