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FORMAT
Description
| Syntax
| Parameters
| Switches
| Related
| Notes
| Examples
| Errorlevels
| Availability
Formats a disk for use with the operating system.
The FORMAT command creates a new root directory and file
allocation table for the disk. It can also check for bad areas on
the disk, and it can delete all data on the disk. In order for
the operating system to be able to use a new disk, you must first
use this command to format the disk.
Syntax
FORMAT
/?
FORMAT
drive:
[/V[:label]]
[[/Q]
| [/AUTOTEST]]
[/FS:file-system]
[[/1]
[/4]
[/8]]
| [/A:size]
| [/F:size]
| [/T:tracks
/N:sectors]
[/B
| /S]
[/C]
[/BACKUP]
[/FORCE]
[[/SELECT
| /U]]
[/X]
[/Z:nn]
Warning: Do not format a floppy disk at a size higher
than it was designed for. For more information, see
Formatting a floppy disk.
Parameters
- drive:
(v1.0
Win95
NT3.1)
- Specifies the drive containing the disk you want to format. You
must specify a drive parameter. If you do not specify any of
the switches, FORMAT uses the drive type to determine
the default format for the disk.
- If the disk was previously formatted and you do not use the
/U switch, the old file allocation table
and root directory are saved to allow unformatting of the disk
if necessary. If you realize that you formatted the wrong disk,
use the UNFORMAT
command as soon as possible.
Switches
- /?
(NTXP)
- Display help.
- /1
(v1.0
Win95
NT3.1 through
NT2000)
- Formats a single side of a floppy disk.
- /4
(v1.0
Win95
NT3.1 through
NT2000)
- Formats a 5.25-inch, 360K, double-sided, double-density
floppy disk on a 1.2-MB disk drive. Some 360K drives cannot
reliably read disks formatted with this switch. When used with
the /1 switch, this switch formats a
5.25-inch, 180K, single-sided floppy disk.
- /8
(v1.0
Win95
NT3.1 through
NT2000)
- Formats a 5.25-inch disk with 8 sectors per track. This
switch formats a floppy disk to be compatible with DOS
versions earlier than v2.0.
- /AUTOTEST
(v4.0)
- UNDOCUMENTED. Do NOT prompt for input or show warning
messages. Can be used in conjunction with the
/U, /S, and
/F switches. It is not compatible with
/Q (causes error message) and
/V is ignored.
- /A:size
(NT3.1)
- Allocation unit size.
- Default settings (via /F) are
strongly recommended for general use.
- FAT supports 8192, 16K, 32K, 64K,
(128K, 256K for sector size > 512 bytes)
Number of clusters <= 65526.
- FAT32 supports 512, 1024, 2048, 4096, 8192, 16K, 32K, 64K,
(128K, 256K for sector size > 512 bytes)
65526 < Number of clusters < 268435446.
- NTFS supports 512, 1024, 2048, 4096, 8192, 16K, 32K, 64K
(compression is not supported for allocation unit sizes
> 4096).
- /B
(v1.0
Win95 through
Win98)
- Reserves space for the system files IO.SYS and MSDOS.SYS (as
hidden files) on a newly formatted disk. In previous versions of
DOS, it was necessary to reserve this space before using the
SYS command to copy the system files to the disk. This switch is
maintained in DOS
v6.0 for
compatibility reasons only.
- /BACKUP
(v4.0)
- UNDOCUMENTED. Similar to
/AUTOTEST. Asks for Volume label and
displays number of bytes available.
- /C
(v6.2
Win95)
- Retests bad clusters. By default, if a drive contains
clusters that have been marked as "bad", FORMAT does not retest
the clusters; it simply leaves them marked "bad". Use the /C
switch if you want FORMAT to retest all bad clusters on the
drive. (In previous versions of DOS, FORMAT always retested
any bad clusters.)
- (NT4)
- Compression - files added to the new disk will be
compressed. NTFS compression is not supported for allocation
units above 4096.
- /F:size
(v4.0
Win95
NT3.1)
- Specifies the size of the floppy disk to format. When possible,
use this switch instead of the /T and
/N switches. Use one of the
values for size:
SIZE size sides density 3.5 / 5.25
160[K[B]] 160KB, single, double, 5.25
180[K[B]] 180KB, single, double, 5.25
320[K[B]] 320KB, double, double, 5.25
360[K[B]] 360KB, double, double, 5.25
640 NT2000
720[K[B]] 720KB, double, double, 3.5
1200[K[B]]
1.2[M[B]] 1.2MB, double, quadruple, 5.25
1.23 NT2000
1440[K[B]]
1.44[M[B]] 1.44MB, double, quadruple, 3.5
2880[K[B]]
2.88[M[B]] 2.88MB, double, extra-high, 3.5
20.8[M[B]] 20.8MB, floptical (mag-op), 3.5
SIZE size sides density 3.5 / 5.25
- /FORCE
(NTXP)
- UNDOCUMENTED. ?
Thanks to Menachem Shapiro!
- /FS:file-system
(NT3.1)
- The file system (FAT, FAT32 or NTFS).
The NTFS file system does not function on floppy disks.
- /N:sectors
(v3.30
Win95
NT3.1)
- Specifies the number of sectors per track. When possible, use
the /F switch instead of this switch.
You must also use the
/T switch. These two switches provide an
alternative method of specifying the size of the disk being
formatted. You cannot use with /F.
- /Q
(v4.0 OR?
v5.0
Win95
NT3.1)
- Specifies a quick format of a disk. With this switch, FORMAT
deletes the file allocation table (FAT) and the root directory of
a previously formatted disk, but does not scan the disk for bad
areas. Use to format only previously formatted
disks that you know are in good condition.
- /S
(v1.0
Win95 through
Win98)
- Copies the operating system files IO.SYS, MSDOS.SYS, and
COMMAND.COM from your system's startup drive to a newly formatted
disk that you can use as a system disk. If FORMAT cannot find the
operating system files, it prompts you to insert a system
disk.
- /SELECT
(v4.0)
- UNDOCUMENTED. Removes the format from a formatted
disk; press Y then Enter at the pause. No messages displayed.
DOS 4.0x's Setup program used this switch to remove a 12-bit
FAT format from a hard disk before reformatting it with a
16-bit FAT, which allowed use of hard drives bigger than 32
Mb.
- Do not use with /U switch, it
will fill sector 0 with F6h, making the disk unreadable.
- /T:tracks
(v3.30
Win95
NT3.1)
- Specifies the number of tracks on the disk. When possible,
use the /F switch instead of this switch.
You must also use the
/N switch. These two switches provide an
alternative method of specifying the size of the disk being
formatted. You cannot use with /F.
- /U
(v4.0 OR?
v5.0
Win95)
- Specifies an unconditional format of a disk. Unconditional
formatting destroys all existing data on a disk and prevents
you from later "unformatting" the disk. You should use /U if
you have received read and write errors during use of a disk.
For information about unformatting a disk, see the
UNFORMAT command.
- Beginning with
v7.00 and
Win95
ALL formats are unconditional. For BATCH purposes, the
switch is still supported, it just doesn't DO anything.
- /V:[label]
(v1.0
Win95
NT3.1)
- Specifies the volume label. A volume label identifies the
disk and can be a maximum of 11 characters. If you omit the /V
switch or use it without specifying a volume label, the
operating system prompts you for the volume label after the
formatting is completed. If you format more than one disk by
using one FORMAT command, all of the disks will be given the
same volume label. Not compatible with the
/8 switch. For more information about disk
volume labels, see the DIR,
LABEL, and
VOL commands.
- /X
(NT2000)
- Forces the volume to dismount first if necessary.
All opened handles to the volume would no longer be valid.
- /Z:nn
(v7.00)
- UNDOCUMENTED. Specifies the cluster size in multiples of
512 bytes. Valid values on nn are:
- 1 512 bytes
- 2 1024 bytes
- 4 2048 bytes
- 8 4096 bytes
- 16 8192 bytes
- 32 16Kb
- 64 32Kb
Related
For information about restoring disks after using the FORMAT
command, see the UNFORMAT
command.
Disk Administrator -
%SYSTEMROOT%\system32\windisk.exe.
GDISK - Ghost Disk, a popular 3rd party tool.
WINNT /O - Create a set of boot floppies
(NT 4.0).
Equivalent Linux BASH commands:
fdformat - Low-level format a floppy disk.
fdisk - Partition table manipulator for Linux.
Notes
Formatting a floppy disk
Do not format a floppy disk at a size higher than it was
designed for. For example, do not format a 360K floppy disk at
1.2MB.
Attempting to format a 720K floppy as 1.4 Mb may give the
rather unhelpful error:
"The type of the file system is RAW. Invalid media or Track
0 bad - disk unusable."
Also, if you use the FORMAT command without specifying the size
of the floppy disk, the operating system will format the floppy
disk at the disk capacity of the disk drive. Thus, if you format
a floppy disk without specifying the size, be careful not to use
a floppy disk smaller than the capacity of the disk drive.
Typing a volume label
After formatting a floppy disk, FORMAT displays the
message:
Volume label (11 characters, ENTER for none)?
The volume label can be a maximum of 11 characters (including
spaces). If you do not want your disk to have a volume label, press
ENTER. For information about volume labels, see the
LABEL command.
Formatting a hard disk
When you use the FORMAT command to format a hard disk, the
operating system displays a message,
before attempting to format the hard disk:
WARNING, ALL DATA ON NON-REMOVABLE DISK
DRIVE x: WILL BE LOST!
Proceed with Format (Y/N)?_
To format the hard disk, press Y; if you do not want to format
the disk, press N.
Beginning with
v4.0, you will be
prompted for a volume label before formatting your hard disk.
FORMAT messages
When formatting is complete, the operating system displays
messages showing the total disk space, any space marked as
defective, the total space used by the operating system (if you
used the /S or
/B switch), and the space
available for your files.
Safe formatting
If you do not specify the /U
switch or a switch that reformats the disk to a different size,
FORMAT performs a "safe" format. It clears the file allocation
table and root directory of the disk but does not delete any data.
You can then use the UNFORMAT
command to recover the disk if you did not intend to format the
disk. FORMAT also checks each sector on the disk to ensure that the
sector can properly store data. If it locates a sector that cannot
store data, FORMAT marks that sector to prevent the operating system
from using it.
If you specify the /U switch
or any switch that changes the size of the disk, FORMAT performs an
unconditional format by deleting all data on the disk.
Quick formatting
You can speed up the formatting process by using the
/Q switch. Use this switch only if
you have not received read or write errors on your disk. You can
speed up the process even more by using both the
/Q and
/U switches. If you use the
/U switch, FORMAT does not save
the information necessary to later unformat the disk.
Formatting a new disk
When you use FORMAT to format a disk that has never been
formatted, you can specify the switches
/U
/C to reduce formatting time.
If you are using DriveSpace and don't often use compressed
floppies, you might also want to disable the AutoMount feature to
further reduce formatting time. To do this, use the
DRVSPACE
/AUTOMOUNT command, or turn off the Automount option in the
Options dialog (start DriveSpace, and then choose Options from the
Tools menu).
Using format with a SUBST drive or a network drive
You should not use the FORMAT command on a drive prepared by
using the SUBST command. You cannot
format disks over a network or an Interlnk drive.
Examples
To format a new floppy disk in drive A using the default size,
type:
FORMAT A:
To perform a quick format on a previously formatted disk in
drive A, type:
FORMAT A: /Q
To format a floppy disk in drive A, completely deleting all data
on the disk, type:
FORMAT A: /U
To format a 360K floppy disk in drive A and copy the operating
system files to the disk to make it a system disk, type:
FORMAT A: /F:360 /S
To format a floppy disk in drive A and assign to it the volume
label "DATA", type:
FORMAT A: /V:DATA
Errorlevels
- 0 The format operation was successful
- 1 Incorrect parameters. NTXP
- 3 The user pressed CTRL+C (^C) or CTRL+BREAK (^BREAK) to stop the process.
THROUGH NT2000
- 4 A fatal error occurred (any error other than 0, 1, 3, or 5)
- 5 The user pressed N in response to the prompt:
"Proceed with Format (Y/N)?" to stop the process
Availability
- External
-
- DOS
-
v1.0
v1.05
v1.1
v1.11
v1.24
v1.25
v1.85
v2.0
v2.01
v2.05
v2.10
v2.11
v2.11R
v2.12
v2.2
v2.25
v3.0
v3.20
v3.05
v3.1
v3.21
v3.25
v3.30
v3.3A
v3.3R
v3.3T
v3.31
v3.40
v4.0
v4.01
v4.01A
v5.0
v5.0A
v5.00.02
v5.001A
v5.01
v5.02
v6.0
v6.10
v6.2
v6.21
v6.22
v6.23
v7.00
v7.0R1
v7.10
v8.00
- Windows
-
Win95
Win98
WinME
- Windows NT
-
NT3.1
NT3.5
NT3.51
NT4
NT2000
NTXP
NT2003
Last Updated: 2006/12/01
Direct corrections or suggestions to:
Rick Lively