                  MS-DOS 5.00-7.00 UNDOCUMENTED FEATURES


                            COMMAND /F SWITCH


  COMMAND.COM /F removes the "Abort, Retry, Fail" message and forces a
"Fail" response to all "Abort, Retry, Fail" prompts issued by the DOS
critical error handler. If the floppy disk is not ready it automatically
goes to Fail. This switch can be used on the CONFIG.SYS file SHELL= line.
Example:
SHELL=C:\COMMAND.COM C:\ /E:512 /P /F

The /F parameter can also be used on a Windows PIF command line, or/and
at the plain DOS prompt:
COMMAND /F

NOTE: To become familiar with COMMAND.COM's command line switches:
1. Users of Windows 95, read the text file CONFIG.TXT (the "SHELL" and
the "COMMAND" topics), located in your Win95 folder (usually \WINDOWS).
2. Users of Win3.1x/MS-DOS 6.xx, run this command from a DOS prompt:
HELP COMMAND
and read the topic.

* BUG REPORT: Using VSHIELD 2.2.2 with PKZIP is a PROBLEM when using
              the "COMMAND.COM /F" parameter (as quoted from WinZip's
              6.1 help files):

"Apparently PKZIP had trouble detecting a floppy disk change. There are
two known reasons for this:
1. Running VSHIELD 2.2.2 (from McAfee Associates) under Windows 95 with
the /ANYACCESS parameter.
2. When using multiple disk spanning under some Windows NT 3.51
configurations with the "no format or erase" or "wipe files" options, NT
does not tell PKZIP about floppy disk changes. This problem occurs
regardless of whether WinZip is running, and occurs only under NT, NOT
under Windows 95 or Windows 3.1.
GENERAL SOLUTION: In both cases you can circumvent the problem with one
extra keystroke as follows: when the message "Insert Disk 2" is
displayed, remove the disk currently in the drive and press the Enter
key before inserting the next disk, in other words, press the Enter key
with no disk in the drive, rather than after inserting the second disk.
An Abort, Retry, Ignore message will be issued. Insert the next disk
and press the "R" key to continue.
SOLUTION FOR VSHIELD USERS: by default, the installation program for
SCAN95 inserts a command into your AUTOEXEC.BAT to run VSHIELD with the
/ANYACCESS parameter. If you are comfortable modifying your AUTOEXEC.BAT
you can change the /ANYACCESS parameter to /FILEACCESS, and the problem
should no longer occur.
IMPORTANT: do not change your autoexec.bat file unless you have a backup
and know how to use it. NOTE that you must re-start your computer for
this change to take effect."

* THE ABOVE BUG REPORT APPEARS COURTESY OF:
  bluetic@access.mountain.net (Mark Richarson)


                            FDISK /MBR SWITCH


  FDISK /MBR repairs a damaged boot sector by overwriting it with a fresh
copy (writes a new Master Boot Record to the hard disk without altering the
partition table information).

WARNING: Writing the master boot record to the hard disk in this manner can
make certain hard disks partitioned with SpeedStor unusable. It can also
cause problems for some dual-boot programs (including Windows 95), or for
disks with more than 4 partitions !!!

The DEFINITION of MBR: at the end of the ROM BIOS bootstrap routine the BIOS
will read and execute the first physical sector of the first floppy or hard
drive on the system.
This first sector of the hard disk is called the Master Boot Record (MBR),
or Partition Table or Master Boot Block. At the beginning of this sector of
the hard disk is a small program. At the end of this sector is where the
partition table is stored. This program uses the partition information to
determine which partition is bootable (usually the first primary DOS
partition) and attempts to boot from it.

NOTE: The biggest partition MS-DOS 6.22 and Windows 95 versions of FDISK can
      create/recognize is 2GB.

WINDOWS 95 USERS: MBR REFRESH

Undocumented! There is a problem when installing a new hard drive on your
system under Win95. If you upgraded from MS-DOS 5.0 (or earlier), your
primary hard disk, formated under your old version of DOS, contains the MBR
(Master Boot Record, also called the boot sector) written by the hard disk
formatting utility (FDISK) provided by MS-DOS. When you add another hard disk
under Win95, you format and partition it with the Win95's (MS-DOS 7.00)
version of FDISK.
This means that each drive was formatted and partitioned under a different
OS. Windows 95 WON'T RECOGNIZE YOUR NEWLY INSTALLED DRIVE! There is nothing
wrong, don't panic. It's a glitch in the OS (something that Microsoft
overlooked)!
When a drive is formatted/partitioned under Win95, the MBR tells the OS that
the drive is a Windows drive. If your drive was formatted/partitioned under
an earlier version of MS-DOS (3.0 and up), the drive is recognized as an
MS-DOS drive.
All you have to do, is to refresh the MBR, by running FDISK (the Windows 95
version) with the undocumented switch /MBR (repairs a boot sector by
overwriting it with a fresh copy), on the old drive. Just run:
FDISK /MBR C:

I presumed that C: is your old drive letter (change if different).
The boot record (MBR) will be refreshed without reformatting the drive!
I presumed that your primary (old) hard disk has assigned the letter C
(single logical partition), and your new (secondary) hard disk is D (also
with a single logical partition). Change the drive letters if different on
your system (and if you have more than one partition per each hard disk).
This can only be done from a DOS prompt, after you exit Win95 to MS-DOS
prompt (or when you boot with the "Command prompt only" option from the
bootup menu).
If the Win95 OS doesn't recognize the new drive, then you can only do this
after rebooting into the old MS-DOS OS (using the dual boot feature
implemented into Win95's OS). This means that you need to have kept your old
MS-DOS 6.xx files (including FDISK) on your primary (old) hard disk.
You also need to have kept the old drive as primary (master) and setup the
new one as secondary (slave).
When you're all done, reboot into Win95. Your newly installed hard drive
should now be recognized by the OS.
Now you can change the new drive to "master" (primary boot drive) and setup
the old one to "slave", especially if the new one is faster.
Sounds pretty complicated, but you may have to do this some day, and it's
better than reformatting the entire drive, and loosing precious data.
There is still another way to refresh the MBR. Run Win95's Scandisk utility
for all hard drives on your system. Scandisk will automatically refresh the
MBR on your drives, if needed (if MBR is damaged).

IMPORTANT: You may also want to read a small article published in PC World
           magazine, the August 1996 issue, at the bootom of page 52, under
           the "Bug Watch" logo. The article title is: "Trouble With Windows
           95's Disk Partitioning". It describes the same above topic with
           more technical details. Also look up PC World's web site at:
           http://www.pcworld.com

UPDATE: There is a great tool that can overcome the above Windows 95
        limitation, and make ANY hard drive compatible with ANY operating
        system, and much more, called Partition Magic 2.0. Sells for about
        30-40 bucks at computer warehouses/stores (it's worth every penny).
        Partition Magic is distributed by PowerQuest. They also have a patch
        available for free, for Partition Magic users (update to the new
        version 2.03), at:
        http://www.powerquest.com/download/update2.html


                             MEM /A SWITCH


  MEM /A displays a short summary screen of your memory configuration and
also the status of the HMA.
HMA (High Memory Area) is a little known 64KB area just above the first
MegaByte (1MB=1024KB=1048576Bytes) of RAM mapped by MS-DOS's HIMEM.SYS
memory manager (or any other 3rd party high/extended memory manager).
Part of DOS itself and of MS-DOS BUFFERS usually load into the HMA.
To display all available memory configuration at a DOS prompt, run:
MEM /A /C /P

NOTE: High DOS is enabled by this CONFIG.SYS line (the "HIGH" switch):
      DOS=HIGH,UMB