Archive bit
Encyclopedia
The archive bit is a file attribute
used by Microsoft operating systems and by OS/2. Typically it's state indicates whether or not the file has been backed up.
When a file is created or modified, the archive bit is set, and when the file has been backed up, the archive bit is cleared. It is by use of the archive bit that incremental backups are possible.
Backup software also provides the option to do a full backup while clearing archive bits - that is, to back up all files irrespective of the archive bit, but to clear the archive bit of all files in the backup for the future. This allows for the creation of an initial full backup that will be supplemented by incremental backups in the future.
The operating system never clears the archive bit on its own, unless explicitly told to do so by the user. In MS-DOS
as well as nearly all versions of Windows
, the archive bit can be seen or changed with the attrib
command-line utility, or by viewing the properties of a given file with the Windows shell
. The archive bit can also be seen or changed with the GetFileAttributes, GetFileAttributesEx and SetFileAttributes Windows APIs.
When a file with a clear archive bit is moved from one place on a file system to another, the archive bit reverts to being set.
Typically, on a computer system that has never been backed up in a manner that clears archive bits, all files on that computer will have their archive bits set, as there are few applications that make use of archive bits without the user's request.
As the archive bit is a file attribute
and not part of the file itself, the contents of the file are unrelated to the status of the archive bit and remain unchanged even if the setting of the archive bit is changed.
File attribute
A file attribute is metadata that describes or is associated with a computer file. For example, an operating system often keeps track of the date a file was created and last modified, as well as the file's size and extension . File permissions are also kept track of...
used by Microsoft operating systems and by OS/2. Typically it's state indicates whether or not the file has been backed up.
When a file is created or modified, the archive bit is set, and when the file has been backed up, the archive bit is cleared. It is by use of the archive bit that incremental backups are possible.
Backup software also provides the option to do a full backup while clearing archive bits - that is, to back up all files irrespective of the archive bit, but to clear the archive bit of all files in the backup for the future. This allows for the creation of an initial full backup that will be supplemented by incremental backups in the future.
The operating system never clears the archive bit on its own, unless explicitly told to do so by the user. In MS-DOS
MS-DOS
MS-DOS is an operating system for x86-based personal computers. It was the most commonly used member of the DOS family of operating systems, and was the main operating system for IBM PC compatible personal computers during the 1980s to the mid 1990s, until it was gradually superseded by operating...
as well as nearly all versions of Windows
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
, the archive bit can be seen or changed with the attrib
Attrib
attrib is a command, in DOS, OS/2 and Microsoft Windows. The function of attrib is to set and remove file attributes...
command-line utility, or by viewing the properties of a given file with the Windows shell
Windows Shell
The Windows shell is the main graphical user interface in Microsoft Windows, and since Windows 95 hosted by Windows Explorer. The Windows shell includes well-known Windows components such as the Taskbar and the Start menu...
. The archive bit can also be seen or changed with the GetFileAttributes, GetFileAttributesEx and SetFileAttributes Windows APIs.
When a file with a clear archive bit is moved from one place on a file system to another, the archive bit reverts to being set.
Typically, on a computer system that has never been backed up in a manner that clears archive bits, all files on that computer will have their archive bits set, as there are few applications that make use of archive bits without the user's request.
As the archive bit is a file attribute
File attribute
A file attribute is metadata that describes or is associated with a computer file. For example, an operating system often keeps track of the date a file was created and last modified, as well as the file's size and extension . File permissions are also kept track of...
and not part of the file itself, the contents of the file are unrelated to the status of the archive bit and remain unchanged even if the setting of the archive bit is changed.