Editing Disk formatting (section)

=== DOS, OS/2 and Windows ===
[[Image:Unformat.gif|thumb|MS-DOS 6.22a FORMAT /U switch failing to overwrite content of partition]]

''format command'': Under [[MS-DOS]], [[PC DOS]], [[OS/2]] and [[Microsoft Windows]], disk formatting can be performed by the <code>[[format (command)|format]]</code> [[command (computing)|command]]. The <code>format</code> program usually asks for confirmation beforehand to prevent accidental removal of data, but some versions of DOS have an undocumented <code>/AUTOTEST</code> option; if used, the usual confirmation is skipped and the format begins right away. The WM/FormatC [[Macro virus (computing)|macro virus]] uses this command to format drive C: as soon as a document is opened.

''Unconditional format'': There is also the <code>/U</code> parameter that performs an ''unconditional'' format which under most circumstances overwrites the entire partition,<ref>{{cite web |url = http://www.mdgx.com/secrets.htm#FORMAT-U |title = AXCEL216 / MDGx MS-DOS Undocumented + Hidden Secrets |access-date = 2008-06-07}}</ref> preventing the recovery of data through software. Note however that the <code>/U</code> switch only works reliably with floppy diskettes (see image to the right). Technically because unless <code>/Q</code> is used, floppies are always low level formatted in addition to high-level formatted. Under certain circumstances with hard drive partitions, however, the <code>/U</code> switch merely prevents the creation of <code>[[unformat (command)|unformat]]</code> 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 editor]]s. Reliance upon <code>/U</code> for secure overwriting of hard drive partitions is therefore inadvisable, and purpose-built tools such as [[DBAN]] should be considered instead.

''Overwriting'': In Windows Vista and upwards the non-quick format will overwrite as it goes. Not the case in Windows XP and below.<ref>
  {{cite web
    | url = http://support.microsoft.com/kb/941961
    | title = MSKB941961: Change in the behavior of the format command in Windows Vista
    | publisher = [[Microsoft Corporation]]
    | quote = 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.
    | date = 2009-02-23
    | access-date = 2012-10-24
  }}
</ref>

''OS/2'': Under OS/2, format will overwrite the entire partition or logical drive if the <code>/L</code> parameter is used, which specifies a ''long'' format. Doing so enhances the ability of [[CHKDSK]] to recover files.