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(*                           UNIT DRIVExx                           *)
(*                                                                  *)
(*                           Version 1.01                           *)
(*                                                                  *)
(*             Copyright (C) 1991 by NativSoft Computing            *)
(*                                                                  *)
(*                         1155 College Ave                         *)
(*                         Adrian, MI 49221                         *)
(*                          (517) 265-6080                          *)
(*                         CIS [71160,1045]                         *)
(*                                                                  *)
(*                Written by:  Charles B. Little, Ph.D.             *)
(*                   Version:  1.01                                 *)
(*             Revision Date:  1 November 1991                      *)
(*                  Language:  Turbo Pascal v6                      *)
(*                                                                  *)
(*                        ALL RIGHTS RESERVED                       *)
(*                                                                  *)
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INTRODUCTION:

DRIVExx is a collection of tools, written in Turbo Pascal v6, for dealing
with block devices in a DOS environment.  To the best of our knowledge, no
such tools exist in any "professional" programming toolboxes, in any
programming language.  The tools available here will allow any Pascal
programmer who uses disk I/O to gain that extra measure of control over his
or her application.  At the very least they will have the ability to
prevent access of a phantom drive so their nice user interface won't get
overwritten by non-interceptable DOS messages like "Insert a disk..."

While it may not be the last word on the subject, DRIVExx works.  And just
about everything you'd want your applications to know about drives is
available WITHOUT ACCESSING THEM!  The only exceptions to hitting drives
are functions DiskWasChanged and GETDPB:  DiskWasChanged will hit a drive
ONLY if the drive supports changeline detection, and GETDPB will hit the
disk only if you tell it to.  Naturally, it is perfectly safe for GETDPB to
hit a removable drive that does not have a disk in it.

Much of the required information is available only in undocumented DOS
functions and data structures.  Wherever a documented function will return
the same information, however, the undocumented function is still used as a
redundancy check.  Indeed, the source code for DRIVExx is probably at least
50% longer than need be due to extensive interlocking redundancy checking.

All of the features of DRIVExx are demonstrated in the demo program
DRVDEMO.PAS.  The only exception to this is function MakeActive, whose
description below should make clear why it is impractical to include it in
DRVDEMO.


If you like it and find it useful you may distribute DRIVExx freely as long
as all files in the original LZH file are distributed.  Those files are:

         DRIVExx.TXT  (this file)
         DRIVExx.TPU  size = 20528, date = 11/1/91, time = 6:00pm
         DRVDEMO.PAS  size = 10034, date = 11/1/91, time = 6:00pm


                                                    NativSoft Computing
                                                    1155 College Ave.
                                                    Adrian, MI  49221