0xF6
as per the INT 1Eh's Disk Parameter Table (DPT) during format on IBM compatible machines. This value is also used on the Atari Portfolio. 8-inch CP/M floppies typically came pre-formatted with a value of 0xE5
,[17] and by way of Digital Research this value was also used on Atari ST and some Amstrad formatted floppies.[nb 6] Amstrad otherwise used 0xF4
as a fill value. Some modern formatters wipe hard disks with a value of 0x00
instead, sometimes also called zero-filling, whereas a value of 0xFF
is used on flash disks to reduce wear. The latter value is typically also the default value used on ROM disks (which cannot be reformatted). Some advanced formatting tools allow configuring the fill value.[nb 7]0xE5
.[17][nb 6] Since the 1990s, most 5.25-inch and 3.5-inch floppies have been shipped pre-formatted from the factory as DOS FAT12 floppies.format
command. The format
program usually asks for confirmation beforehand to prevent accidental removal of data, but some versions of DOS have an undocumented /AUTOTEST
option; if used, the usual confirmation is skipped and the format begins right away. The WM/FormatC macro virus uses this command to format drive C: as soon as a document is opened./U
parameter that performs an unconditional format which under most circumstances overwrites the entire partition,[22] preventing the recovery of data through software. Note however that the /U
switch only works reliably with floppy diskettes (see image to the right). Technically because unless /Q
is used, floppies are always low level formatted in addition to high-level formatted. Under certain circumstances with hard drive partitions, however, the /U
switch merely prevents the creation of unformat
information in the partition to be formatted while otherwise leaving the partition's contents entirely intact (still on disk but marked deleted). In such cases, the user's data remain ripe for recovery with specialist tools such as EnCase or disk editors. Reliance upon /U
for secure overwriting of hard drive partitions is therefore inadvisable, and purpose-built tools such as DBAN should be considered instead./L
parameter, which specifies a long format, then format will overwrite the entire partition or logical drive. Doing so enhances the ability of CHKDSK to recover files.mkfs
command. On Linux (and potentially other systems as well) mkfs
is typically a wrapper around filesystem-specific commands which have the name mkfs.fsname
, where fsname is the name of the filesystem with which to format the disk.[24] Some filesystems which are not supported by certain implementations of mkfs
have their own manipulation tools; for example Ntfsprogs provides a format utility for the NTFS filesystem.FORMAT
command did with floppy diskettes, filling every data sector with the format filler byte value (typically 0xF6
).0xE5
is the reason why the value of 0xE5
has a special meaning in directory entries in FAT12, FAT16 and FAT32 file systems. This allowed 86-DOS to use 8-inch floppies out of the box or with only the FAT initialized./W:246
(for a fill value of 0xF6
). In contrast to other FDISK utilities, DR-DOS FDISK is not only a partitioning tool, but can also format freshly created partitions as FAT12, FAT16 or FAT32. This reduces the risk of accidentally formatting the wrong volume.When you do not specify either the RECOMP or LABEL option, the disk area is initialized by writing a device-dependent number of records (containing binary zeros) on each track. Any previous data on the disk is erased.
The direct access volumes, on which TSS/360 virtual organization data sets are stored, have fixed-length, page size data blocks. No key field is required. The record overflow feature is utilized to allow data blocks to span tracks, as required. The entire volume, with the current exception of part of the first cylinder, which is used for identification, is formatted into page size blocks.
The format command behavior has changed in Windows Vista. By default in Windows Vista, the format command writes zeros to the whole disk when a full format is performed. In Windows XP and in earlier versions of the Windows operating system, the format command does not write zeros to the whole disk when a full format is performed.