Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!seismo!husc6!bu-cs!bucsb.bu.edu!madd
From: madd@bucsb.bu.edu.UUCP (Jim "Jack" Frost)
Newsgroups: comp.sys.ibm.pc
Subject: Re: number of DOS drives
Message-ID: <630@bucsb.bu.edu.UUCP>
Date: Thu, 4-Dec-86 23:29:32 EST
Article-I.D.: bucsb.630
Posted: Thu Dec  4 23:29:32 1986
Date-Received: Fri, 5-Dec-86 06:23:16 EST
References: <2268@sdcsvax.UCSD.EDU> <623@bucsb.bu.edu.UUCP> <1450@isis.UUCP>
Reply-To: madd@bucsb.bu.edu.UUCP (Jim "Jack" Frost)
Organization: ODO (Organization for the Disorganization of Organization)
Lines: 57
Mood: Relatively happy


In article <1450@isis.UUCP> dragheb@isis.UUCP (Darius "OPRDRT" Ragheb) writes:
>In article <623@bucsb.bu.edu.UUCP> madd@bucsb.bu.edu.UUCP (Jim Frost) writes:
>>>
>>>In article <1441@isis.UUCP> dragheb@isis.UUCP (Darius "OPRDRT" Ragheb) writes:
>>>>
>>>>I think this might work (I have not tried it):
>>>>use function (_FUNCTION_, not interrupt) call Eh. It will do two things:
>>>>make the drive selected in DL the current drive, and
>>>>return the number of drives in AL.
>>>>
>>>If you had tried it, you would have found out it *doesn't* work :-) :-)
>
>I think we have it licked now!  I wrote the following program and tested
>it on a PC with 1 drive and  a PC with 2 drives and it returned
>the correct number of floppies:
[ C program deleted ]
>
>What it does is call INT 11h and check bits 6 and 7 in the ax
>register.  (0 means 1 drive, etc).
>
>(BTW REGS is a struct of ints)
>
That's great, but I assumed that they may have at least one hard
drive.  Also, it's at least theoretically possible to have more than 4
floppies (why would you do that?  no idea, but...) so you really can't
trust the configuration bits, which are limited to 4.  Because DOS
allows you to install odd devices (RAM drives, etc) which you might
like to use, you'd probably want to see if there is one available.

I really wish I had my DOS manual, but here is the general idea of how
I would do it (expanded slightly from last time):

* Call DOS to find out how many drives it CAN have (ie LASTDRIVE
  setting).
* Start at LASTDRIVE and request the volume label for all drives down to
  C:.
* If you don't find a drive higher than C:, you could test the
  configuration bits.  This would take care of the nasty "Drive not
  ready error.  Abort, Retry, Ignore?" when you don't have a floppy
  installed.

Come to think of it, you might want to check the bits first to see if
you have an installed floppy that is higher than B:.  This isn't
common, but it's possible.  As for systems with 4+ floppies, well,
tough luck.  Get a hard drive :-).

This is really easy to write if you have the DOS Tech Ref manual
handy, which I don't.  I think that is about as accurate as you could
get without explicitly asking "how many drives/psuedo drives do you
have?"
-- 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
                   - Jim Frost * The Madd Hacker -
UUCP:  ..!harvard!bu-cs!bucsb!madd | ARPANET: madd@bucsb.bu.edu
CSNET: madd%bucsb@bu-cs            | BITNET:  cscc71c@bostonu
-------------------------------+---+------------------------------------
"Oh beer, oh beer." -- Me      |      [=(BEER) <- Bud the Beer (cheers!)