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LW1DSE > TECH 16.12.17 00:32l 185 Lines 6733 Bytes #999 (0) @ WW
BID : 1123-LW1DSE
Read: GUEST
Subj: DOS Hidden Commands
Path: IW8PGT<IZ3LSV<I0OJJ<GB7CIP<LU4ECL<LU9DCE<LU1DBQ<LU7DQP
Sent: 171215/2313Z @:LU7DQP.#LAN.BA.ARG.SOAM #:24787 [Lanus Oeste] FBB7.00i
From: LW1DSE@LU7DQP.#LAN.BA.ARG.SOAM
To : TECH@WW
[¯¯¯ TST HOST 1.43c, UTC diff:5, Local time: Mon Nov 20 18:50:19 2017 ®®®]
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).
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