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LW1DSE > TECH 13.11.11 20:40l 450 Lines 18363 Bytes #999 (0) @ WW
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Subj: DOS: hidden features
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From: LW1DSE@LW8DJW.#1824.BA.ARG.SA
To : TECH@WW
[――― TST HOST 1.43c, UTC diff:5, Local time: Sun Nov 13 09:01:25 2011 ®®®]
COMMAND.COM HIDDEN PARAMETERS
-----------------------------
COMMAND.COM is the MS-DOS mode command line interpreter, located by
default in C:\DOS [MS-DOS 5.0 - 6.22].
IMPORTANT: To become familiar with COMMAND.COM's command line switches (the
documented ones anyway):
All DOS users: run:
COMMAND /?
at any DOS prompt to display the COMMAND.COM help screen.
MS-DOS 6.xx users: run this command from a DOS prompt:
* HELP COMMAND
and read the topic.
NOTE: Read also the "COMMAND.COM" topic.
* COMMAND /D [MS-DOS 5.0 and above ONLY!]
COMMAND /D used on the CONFIG.SYS SHELL= line (the primary shell), or at the
MS-DOS prompt (secondary shell in combination with the COMMAND /P parameter),
prevents the execution of the AUTOEXEC.BAT file at bootup! Example:
SHELL=C:\COMMAND.COM C:\ /E:512 /D /P
* COMMAND /F [MS-DOS 6.00 and above ONLY!]
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 /F /P
* COMMAND /Z [MS-DOS 7.00 and above ONLY!]
COMMAND.COM /Z displays the "ERRORLEVEL" return code messages after executing
each external DOS command (internal DOS commands don't display error codes).
This switch can be used on the CONFIG.SYS file SHELL= line. Example:
SHELL=C:\COMMAND.COM C:\ /E:512 /P /Z
EMM386.EXE HIDDEN PARAMETERS
----------------------------
EMM386.EXE is the Microsoft upper/extended/expanded memory manager, located by
default in C:\DOS [MS-DOS 5.0 - 6.22]. EMM386.EXE can be loaded ONLY in
CONFIG.SYS using the DEVICE command. Example:
DEVICE=drive:\path\EMM386.EXE RAM I=B000-B7FF D=256 AUTO NOTR
EMM386.EXE's DEVICE line MUST appear in Config.sys after the HIMEM.SYS line,
and before ANY other device drivers loaded with DEVICE or DEVICEHIGH!
Running:
* EMM386
from a DOS prompt, displays the EMM386 status.
EMM386.EXE provides access to the Upper Memory Area (UMA), uses the computer's
extended memory to simulate expanded memory and allows programs and device
drivers to load into Upper Memory Blocks (UMBs).
IMPORTANT: To become familiar with EMM386.EXE's command line switches (the
documented ones anyway):
MS-DOS 6.xx users: run this command from any DOS prompt:
* HELP EMM386.EXE
and read the topic.
* DEVICE=drive:\path\EMM386.EXE /NOTR [MS-DOS 6.00 and above ONLY!]
EMM386.EXE's detection code searches for the presence of a Token Ring network
adapter. This detection code may cause some computers to hang. The NOTR switch
can be used to disable this search.
This switch is valid ONLY for EMM386.EXE versions 4.45 - 4.49 [MS-DOS 6.00 -
6.22] up to 4.95 [MS Windows 95 - 98, a.k.a. MS-DOS 7.00 - 7.10a].
Example:
* DEVICE=C:\WINDOWS\EMM386.EXE NOTR
FDISK.EXE HIDDEN PARAMETERS
---------------------------
FAT16 ? FAT32
FAT16 is the most used File Allocation Table standard on "Wintel" PCs,
recognized by all MS-DOS releases begining with 4.00, and by all MS Windows
versions.
MS-DOS releases older than 4.00 operate with the older FAT12 standard,
discontinued. FAT12 was able to handle partitions up to 16 MB (with a 4 KB
cluster size).
FAT16 limitations:
- maximum partition size = 2 GigaByes (GB) = 2,048 MegaBytes (MB);
- (too) large cluster size, which wastes a lot of disk space, by allocating
1 cluster to each file on disk, even if a file is at least 1 byte in length.
Another example: a 33 KB file has 2 clusters assigned on a disk partition with
32 KB clusters, thus wasting 31 KB because 2 files do NOT share the same
cluster:
Partition size: FAT16 Cluster size:
-------------------------------------------
0 - 127 MB 2 KB = 2048 B
128 - 255 MB 4 KB = 4096 B
256 - 511 MB 8 KB = 8192 B
512 - 1023 MB 16 KB = 16384 B
1024 - 2047 MB 32 KB = 32768 B
Begining with the release of Windows 95B OSR 2.0, Microsoft introduced a new
File Allocation Table standard: FAT32, which extends these limits:
- FAT32, first version, supports partitions up to 2 TeraBytes (TB) = 2,048 GB =
= 2,097,152 MB;
- FAT32X, second version, released begining with MS Windows 95C OSR 2.5,
features eXtended support for newer drives larger than 8 GB (with more than
1023 cylinders, 255 heads and 63 sectors), using the new BIOS interrupt 13h
extension (on newer Pentium class and above PCs that support this BIOS feature),
for a total of 28 bits of addressing a maximum of 137 GB of hard disk capacity.
More techno details on FAT32X and the 8 GB BIOS limit:
IBM's "Getting Beyond the ATA 8.4 GB Limit"
The Partition Primer page
The Partition FAQ page
FAT16 + FAT32 explained
- smaller, more efficient cluster size, without noticeable performance
degradation:
Partition size: FAT32/FAT32X Cluster size:
--------------------------------------------------
0 - 259 MB 512 B[*]
260 - 511 MB 1 KB = 1024 B[*]
512 - 8191 MB 4 KB = 4096 B
8192 - 16383 MB 8 KB = 8192 B
16384 - 32767 MB 16 KB = 16384 B
32768 MB - 2 TB 32 KB = 32768 B
[*] = ONLY if using: FORMAT drive: /Z:n!
Therefore FAT32 wastes a lot less disk space, preserving speedy disk access the
same time.
PROs + CONs:
+ Larger cluster size means faster disk access, but more disk overhead (wasted
disk space), and less room for stored files.
Opposite to:
- Smaller cluster size means slower disk access, but less disk overhead (wasted
disk space), and more room for stored files.
NOTE: The performance hit for using FAT32 depends on the speed of your CPU,
disk controller capabilities, and hard disk subsystem transfer rate and access
time.
Below are detailed only the UNDOCUMENTED (hidden) FDISK parameters.
IMPORTANT: To become familiar with FDISK.EXE's command line switches (the
documented ones anyway), run:
* FDISK /?
from any DOS prompt, to display the FDISK.EXE help screen.
FDISK /FPRMT [ 95B OSR2 + MS-DOS 7.10 and above ONLY!]
FDISK /FPRMT enables the use of FAT32 file system on hard disks/partitions
smaller than 512 MB, normally not allowed by default!
NOTE: Use it with CAUTION ONLY from the native MS-DOS command prompt, NOT from
a DOS box/session, even full screen, inside the 9x GUI!
FDISK x /PRI:ps /EXT:es /LOG:ls [MS-DOS 6.00 and above ONLY!]
FDISK x /PRI:ps /EXT:es /LOG:ls meaning:
x = drive number: 1, 2, 3... etc. Drive 1 corresponds to the 1st hard disk
installed on your machine: C, D, E... etc.
/PRI:ps = creates a primary partition of size... (in MegaBytes).
/EXT:es = creates an extended partition of size... (in MegaBytes).
/LOG:ls = creates a logical drive in the extended partition of size... (in
MegaBytes).
If using FAT16, the maximum size... allowed is 2,047 MB (2 GigaBytes).
If using FAT32, the maximum size... allowed is 2,047 GB (2 TeraBytes).
NOTES:
Only one FDISK "LOG" is allowed per EACH logical drive! Therefore on machines
with more than one logical drive, you MUST run an:
FDISK x /LOG:ls
command separately for each drive in your system.
You MUST have 95 B/C OSR 2.x or 98 to use FAT32.
FDISK /MBR [MS-DOS 6.00 and above ONLY!]
FDISK /MBR repairs a damaged boot sector by overwriting it with a fresh copy,
writing a new Master Boot Record to the boot hard disk without altering the
partition table information.
WARNING: Writing the master boot record to the hard disk in this manner can
render certain hard disks partitioned with SpeedStor unusable! It can also
cause problems for some dual-boot programs (including 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 largest partition MS-DOS begining with release 3.00 and up to 95a
OSR1 versions of FDISK can create/recognize is 2 GB (GigaBytes).
The 2 GB partition limit has been overcome by Microsoft (FINALLY!), begining
with 95B OSR2. Named the FAT32 file system, it supports partitions/drives up
to 2 TB (TeraBytes).
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, formatted 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.
95 WON'T RECOGNIZE YOUR DRIVE! There is nothing wrong, don't panic. :) It's
"just" another glitch in the OS, something Microsoft overlooked!
When a drive is formatted/partitioned under Win95, the MBR tells the OS that
the drive is a 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 95 version)
with the UNDOCUMENTED /MBR switch (repairs a boot sector by overwriting it with
a fresh copy), on the old drive. Just run:
FDISK /MBR C:
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 the real mode MS-DOS prompt, after you exit Win95
to MS-DOS (or when you boot with the "Command prompt only option from the
bootup menu).
NOTE: Looks like the "MBR BUG" does NOT affect OSR2 or 98.
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 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).
Reboot your system when done. Your (newly installed) hard drive should be
recognized by the OS from now on.
Now you can change the new drive to "master" (primary boot drive) and setup the
old one as "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 losing 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, as needed (if the MBR is damaged).
UPDATE: There is a great tool that can overcome the above 95 limitation, and
make ANY hard drive compatible with ANY operating system and ANY FAT system
(and much more), called Partition Magic by Powerquest Retails for about 30-50
bucks at popular computer stores (it's worth every penny, it saved my
"computing life" more than once).
Partition Magic new version 4.0 supports OSR2/Win98 FAT32/FAT32X and
WinNT 32-bit NTFS file system standards.
FDISK /Q [MS-DOS 6.00 and above ONLY!]
FDISK /Q prevents rebooting the computer automatically after altering the
partition information by using FDISK with other parameters.
FDISK /STATUS [MS-DOS 5.00 and above ONLY!]
FDISK /STATUS displays a screen similar to using FDISK's option 4:
"Partition information", but also includes EXTENDED partition information.
FORMAT.COM HIDDEN PARAMETERS
----------------------------
IMPORTANT: To become familiar with FORMAT.COM's command line switches (the
documented ones anyway), run:
FORMAT /?
from any DOS prompt, to display the FORMAT.COM help screen.
FORMAT /AUTOTEST [MS-DOS 5.0 and above ONLY!]
This parameter makes FORMAT.COM check for the existing format of your disk,
unless the /U (UNCONDITIONAL) parameter is also used [MS-DOS 5.00 - 6.xx ONLY],
and then proceeds with an UNATTENDED DISK(ETTE) FORMAT:
DOESN'T prompt for a volume label!
DOESN'T prompt to format another disk(ette)!
There is NO delay: NO user intervention!
Ends WITHOUT pausing!
After completion, it DOES display disk space statistics.
WARNING: This procedure works on hard drives as well as floppy drives!
FORMAT drive: /BACKUP [MS-DOS 5.0 and above ONLY!]
This FORMAT.COM parameter works exactly like /AUTOTEST, but it DOES prompt the
user for a volume label, and it DOES display disk space information upon
completion.
FORMAT drive: /SELECT [MS-DOS 5.00 and above ONLY!]
This FORMAT.COM parameter is similar to using the MIRROR command [MS-DOS 5.00
and earlier ONLY!].
NOTE: Microsoft removed MIRROR.COM from all MS-DOS releases begining with 6.00.
FORMAT drive: /U [MS-DOS 5.0 and above ONLY!]
This FORMAT.COM parameter performs an UNCONDITIONAL format, which DESTROYS
every byte of data on ANY hard disk/floppy by overwriting it with hex F6h.
WARNING: You CAN'T UNFORMAT a disk(ette) formatted using the /U option!
FORMAT drive: /SELECT /U [MS-DOS 5.00 and above ONLY!]
This particular combination of FORMAT.COM parameters makes a disk(ette)
UNREADABLE!
WARNING: DO NOT use these two FORMAT switches TOGETHER on ANY drive!
FORMAT drive: /Z:n [ 95B OSR 2.0 + MS-DOS 7.10 and above ONLY!]
FORMAT drive: /Z:n formats a FAT32 drive with a cluster size of n times 512
Bytes.
Meaning:
drive: = your hard drive letter: C:, D:, E:... etc.
n = number of sectors per cluster multiplied by 512 = cluster size in Bytes.
Examples:
n = 1 creates a 512 Bytes cluster;
n = 2 creates a 1024 Bytes (1 KB) cluster;
n = ? creates a ? x 512 = ???? Bytes (???? Bytes : 1024 = ? KB) cluster.
You can modify the size of the allocation units (sectors) on a FAT32 drive to
your heart desire.
WARNING: It is recommended NOT to change the default cluster size, because some
programs such as disk-repair/anti-virus tools might NOT work properly!
HIMEM.SYS HIDDEN PARAMETERS
---------------------------
HIMEM.SYS is the Microsoft high/upper/extended memory manager, located by
default in C:\ [ 95 - 98], or in C:\DOS [MS-DOS 5.00 - 6.22].
/WfWG can't start without HIMEM.SYS loaded!
HIMEM.SYS can be loaded ONLY in CONFIG.SYS using the DEVICE command. Example:
DEVICE=drive:\path\HIMEM.SYS /TESTMEM:OFF /Q
HIMEM.SYS's DEVICE line MUST appear in Config.sys before ANY other device
drivers loaded with DEVICE or DEVICEHIGH, including EMM386.EXE!
HIMEM.SYS provides access to the High Memory Area (HMA), Upper Memory Area
(UMA) and coordinates the use of the computer's extended memory, so that no two
programs or device drivers use the same memory area at the same time.
IMPORTANT: To become familiar with HIMEM.SYS's command line switches (the
documented ones anyway):
MS-DOS 6.xx users: run this command from any DOS prompt:
HELP HIMEM.SYS
and read the topic.
NOTE: Read also the HIMEM.SYS related topics in MEMORY.TXT and EMM386.TXT,
both part of my Win9x/DOS7 χTricks + Secrets files [W95-11D.ZIP]
DEVICE=drive:\path\HIMEM.SYS /Q [MS-DOS 6.00 and above ONLY!]
The HIMEM.SYS /Q parameter (QUIET) does NOT allow the display of HIMEM.SYS
loading status during bootup. Only error messages will be shown, IF the:
Logo=0
line exists in MSDOS.SYS, under the [Options] section, valid ONLY for 95 -
98 OS.
This switch is valid ONLY for HIMEM.SYS versions 3.10 [MS-DOS 6.xx] up to 3.54
[MS 9x].
Example:
DEVICE=C:\\HIMEM.SYS /Q
MEM.EXE HIDDEN PARAMETERS
-------------------------
IMPORTANT: To become familiar with MEM.EXE's command line switches (the
documented ones anyway), run:
MEM /?
from any DOS prompt, to display the MEM.EXE help screen.
MEM /A [MS-DOS 6.00 and above ONLY!]
MEM /A (ALL) displays a short summary screen of your memory configuration and
also the status of the HMA.
HMA (High Memory Area) is a little known 64 KB area just above the first
MegaByte (1 MB = 1,024 KB = 1,048,576 Bytes) of RAM mapped by Microsoft
HIMEM.SYS memory manager (or another 3rd party upper/extended/expanded memory
manager, like Quarterdeck QEMM386, Helix NetRoom RM386, Qualitas 386MAX etc).
Part of DOS module itself and of MS-DOS BUFFERS usually load into the HMA.
Example of MEM /A output display (only the HMA info is shown here):
"Available space in High Memory Area 1K (944 bytes)
MS-DOS is resident in the high memory area."
To display ALL available memory configuration at a DOS prompt, run:
MEM /A /C /P
or if you prefer technical details (conventional/upper memory regions map and
exact hex addresses where all loaded devices/drivers/TSRs reside), run:
MEM /D /P
NOTE: High DOS is enabled by this CONFIG.SYS line (the "HIGH" switch):
DOS=HIGH,UMB
VER HIDDEN PARAMETERS
---------------------
VER /R [MS-DOS 5.0 and above ONLY!]
VER is an internal MS-DOS command, built into COMMAND.COM. An actual file does
not exist.
VER /R (REVISION) displays extended DOS info:
the DOS revision and the memory location of the DOS module, in addition to
using the plain VER command.
Example of screen output for VER command (using Win95B OSR2 + MS-DOS 7.10):
" 95. [Version 4.00.1111]"
Example of screen output for VER /R command (using Win95B OSR2 + MS-DOS 7.10):
" 95. [Version 4.00.1111]
Revision A
DOS is in HMA"
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