From: "Ilya P. Ryzhenkov" <ILYA AT spy DOT isp DOT nsc DOT ru>
Organization:  ISPh SB RAS
To: Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
Date:          Fri, 25 Oct 1996 11:54:08 GMT+0600
Subject:       Re: Drive Help
CC: djgpp AT delorie DOT com
Message-ID: <2850CD3323@spy.isp.nsc.ru>

RI> Date sent:      Thu, 24 Oct 1996 14:04:44 +0200 (IST)
RI> From:           Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>

RI> > There is also other soft which creates it's
RI> > own drives regardles of what is actually present on a machine and in
RI> > DOS mind ;-) (Examples : mscdex, norton utilities diskreet, 
RI> > ramdisk...)
RI> 
RI> As long as that software abides by the rules of DOS block devices, they 
RI> will all present the above behavior.  For example recall that if Novell 
RI> Netware wants to create drive R:, you are told to put LASTDRIVE = R into 
RI> CONFIG.SYS.  
 I DO use Novell Netware and netx dos requester
 and it DO require lastdrive to be LESS then first network drive.
 netx always map LOGIN directory AFTER the lastdrive letter.
 That is experimental fact. if lastdrive==Z you will be not able to 
 access network in any way. However, if you'll use VLM requester,
 you can map only drives less or equal to lastdrive. It only depends
 on soft, not DOS.
 
RI> That command tells DOS to allocate all the drives from A: to 
RI> R:.  As another example, recall that MSCDEX always defines the first 
RI> drive letter beyond all the real disk drives, it never leaves a drive 
RI> letter in between.
 I do use mscdex in my machine, and there is one floppy, and 
 one partition (i.e. A: C:) and mscdex defines letter E: (as said
 in command line) for cd-rom.
 Any comments ?
 
 Yes you right in the fact, that DOS allocates info structures for
 ALL drives from A: to LASTDRIVE: , but it's only caused by index
 method of access to drives.
 The common way to identify if DOS drive is present is to
 make a set_current_drive. Then make a get_current_drive, and if
 result is equal to setted - drive is present. This way most of
 DOS commanders and shells work (Norton Commander, Volkov Commander,
 DOS Navigator, etc...)
 
 
======================================================================
Institute of Semiconductors Physics                Ilya P. Ryzhenkov 
Russian Academy of Sciencies             e-mail: ilya AT spy DOT isp DOT nsc DOT ru
Siberian Branch                          http://spy.isp.nsc.ru