Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!ncar!noao!arizona!naucse!wew
From: wew@naucse.UUCP (Bill Wilson)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Magic Number Five in turbo C, MS C, and int 21/0E
Message-ID: <1748@naucse.UUCP>
Date: 16 Oct 89 15:49:57 GMT
References: <483@schaefer.MATH.WISC.EDU>
Organization: Northern Arizona University, Flagstaff, AZ
Lines: 38

From article <483@schaefer.MATH.WISC.EDU>, by wayne@schaefer.MATH.WISC.EDU (Rick Wayne):
> we've run into a little problem here that i find baffling.  we're trying to
> determine the number of disk drives on a machine at runtime.  there's a DOS
> interrupt service for this: interrupt 0x21, function 0x0E, "set default
> disk drive".  it's supposed to return the number of drives in the system.
> 
> for all the machines we have here (AST Premium 386, Standard 286, Compaq
> Deskpro, Dell 210), we get the answer of...five.  needless to say, these
> disparate machines have differing numbers of drives.  the one number we
> CANNOT come up with, of course, is five.
>
I tried out the function and it worked just fine on my system.  The
function returns the number of drives that DOS thinks you have.  Since
I have the following in my config.sys:
   lastdrive=z
the function reports 26.  You may want to check your config for what
is indicated in it.  I used the following code to check:

#include <stdlib.h>
#include <stdio.h>
#include <dir.h>

main()
{
   int ndrvs;

   ndrvs=setdisk(getdisk());
   printf("# of drives is %d\n",ndrvs);
}

I use getdisk so that I do not change the current drive.

 
-- 
Let sleeping dragons lie........               | The Bit Chaser
----------------------------------------------------------------
Bill Wilson             (Bitnet: ucc2wew@nauvm | wilson@nauvax)
Northern AZ Univ  Flagstaff, AZ 86011