BACKUP (MS-DOS) - Revision history

Jsummers: /* Software */

2025-08-23T12:44:25Z

‎Software

Jsummers at 16:25, 5 July 2025

2025-07-05T16:25:37Z

Jsummers at 17:59, 4 July 2025

2025-07-04T17:59:02Z

Jsummers at 17:33, 4 July 2025

2025-07-04T17:33:53Z

Sembiance: sample files

2024-06-15T00:31:17Z

sample files

Jsummers: Category:MS-DOS

2017-03-29T16:22:16Z

Category:MS-DOS

Dan Tobias at 02:13, 18 February 2017

2017-02-18T02:13:03Z

Jsummers at 16:28, 29 March 2016

2016-03-29T16:28:02Z

Dan Tobias: Created page with "{{FormatInfo |subcat=Archiving }} The '''BACKUP''' command in MS-DOS backed up the contents of a hard disk to files of a proprietary, undocumented format which could be retur..."

2013-03-27T02:53:58Z

Created page with "{{FormatInfo |subcat=Archiving }} The '''BACKUP''' command in MS-DOS backed up the contents of a hard disk to files of a proprietary, undocumented format which could be retur..."

New page

{{FormatInfo
|subcat=Archiving
}}

The '''BACKUP''' command in MS-DOS backed up the contents of a hard disk to files of a proprietary, undocumented format which could be returned to their original file structure using the RESTORE command. A number of different formats have been used in different versions of DOS. Files generally had extensions consisting of three digits (incremented consecutively across the files of the backup set), with a control file called ''BACKUPID.@@@''. The aim was to store the entire file and directory structure of a disk onto a set of files that each fit on a floppy disk.

The developers of FreeDOS have attempted to reverse-engineer these formats to produce backup and restore commands in that system that are compatible with Microsoft's.

== Links ==
* [http://www.ibiblio.org/pub/micro/pc-stuff/freedos/files/dos/restore/brtecdoc.htm Tech docs from FreeDOS]
* [http://www.computerhope.com/backup.htm Backup command help]

[[Category:Microsoft]]

@@ Line 38: / Line 38: @@
 * [https://winworldpc.com/product/ms-dos/3x MS-DOS], at WinWorld
 * MS-DOS 4.0 source code: [https://github.com/microsoft/MS-DOS/tree/main/v4.0/src/CMD/BACKUP BACKUP], [https://github.com/microsoft/MS-DOS/tree/main/v4.0/src/CMD/RESTORE RESTORE]
 == Sample files ==

@@ Line 1: / Line 1: @@
 {{FormatInfo
 |subcat=Backup
-|extensions={{ext|@@@}}, {{ext|@02}}, {{ext|001}}, others
+|extensions={{ext|@@@}}, {{ext|@01}}, {{ext|001}}, others
 }}
-The '''BACKUP''' command in MS-DOS backed up the contents of a hard disk to files of a proprietary, undocumented format which could be returned to their original file structure using the RESTORE command.
+Some versions of [[MS-DOS]] have a '''BACKUP''' command, whose main use is to back up some or all of the contents of a hard disk to a set of floppy disks. The '''RESTORE''' command is used to restore files. The backup format was undocumented.
 There are at least two quite different formats:
@@ Line 13: / Line 13: @@
 == Format details ==
 === Format details - 2.0 ===
-<!-- Files generally had extensions consisting of three digits (incremented consecutively across the files of the backup set), with a control file called ''BACKUPID.@@@''. The aim was to store the entire file and directory structure of a disk onto a set of files that each fit on a floppy disk. -->Backed up files usually keep their original filenames. The data is modified, to add a header. In case of a duplicate filename (because the same filename appeared in different directories), a replacement extension like '''.@02''' is used. A file may be split into multiple backup files, each containing a fragment of its data.
+Backed up files usually keep their original filenames. The data is modified, at least to add a header. In case of a duplicate filename (because the same filename appeared in different directories), a replacement extension like '''.@01''' or '''.@02''' is evidently used. A file may be split into multiple backup files, each containing a fragment of the original data.
 An extra BACKUPID.@@@ file is written to each disk, containing general information about the backup. It doesn't contain any critical information.
@@ Line 22: / Line 22: @@
 == Identification ==
 === Identification - 2.0 ===
-BACKUPID.@@@: (TODO)
+BACKUPID.@@@: The first byte of the file is either {{magic|0xff}} or {{magic|0x00}}. The file is exactly 128 bytes in size. (TODO: More info)
-Data files: It's possible to heuristically identify these files from their contents, but they don't really have any distinctive markings. (TODO)
+Data files: It's possible to heuristically identify data files from their contents, but they don't really have any distinctive markings. The first byte of a file is either {{magic|0xff}} or {{magic|0x00}}. Non-fragmented archives start with bytes {{magic|ff 01 00}}. (TODO: More info)
 === Identification - 3.3 ===
@@ Line 47: / Line 47: @@
 .3 format:
 * &#x7b;{{CdTextfiles|pcblueii/PCBLUE/VOL583.ZIP|VOL583.ZIP}}, {{CdTextfiles|pcblueii/PCBLUE/VOL584.ZIP|VOL584.ZIP}}&#x7d; → ...
 == Links ==

@@ Line 19: / Line 19: @@
 === Format details - 3.3 ===
 Just two files are written to each floppy disk: CONTROL.001 (or .002, etc.), and BACKUP.001 (.002, etc.). The CONTROL file contains information about the file data in the corresponding BACKUP file.
 == Specifications ==
-* [http://www.ibiblio.org/pub/micro/pc-stuff/freedos/files/dos/restore/brtecdoc.htm Tech docs from FreeDOS]
+* [https://www.ibiblio.org/pub/micro/pc-stuff/freedos/files/dos/restore/brtecdoc.htm Tech docs from FreeDOS]
-* One could presumably learn about the format(s) from the MS-DOS 4.0 source code, listed below.
+* One could presumably learn about at least one of the formats from the MS-DOS 4.0 source code, listed below.
 == Software ==
@@ Line 29: / Line 40: @@
 == Sample files ==
 * {{DexvertSamples|archive/dosBackupFile}}
 == Links ==

@@ Line 1: / Line 1: @@
 {{FormatInfo
 |subcat=Backup
-|extensions={{ext|@@@}}, others
+|extensions={{ext|@@@}}, {{ext|@02}}, {{ext|001}}, others
 }}
-The '''BACKUP''' command in MS-DOS backed up the contents of a hard disk to files of a proprietary, undocumented format which could be returned to their original file structure using the RESTORE command. A number of different formats have been used in different versions of DOS. Files generally had extensions consisting of three digits (incremented consecutively across the files of the backup set), with a control file called ''BACKUPID.@@@''. The aim was to store the entire file and directory structure of a disk onto a set of files that each fit on a floppy disk.
+The '''BACKUP''' command in MS-DOS backed up the contents of a hard disk to files of a proprietary, undocumented format which could be returned to their original file structure using the RESTORE command.
-The developers of FreeDOS have attempted to reverse-engineer these formats to produce backup and restore commands in that system that are compatible with Microsoft's.
+There are at least two quite different formats:
 == Sample files ==
@@ Line 11: / Line 32: @@
 == Links ==
 * [http://www.computerhope.com/backup.htm Backup command help]
@@ Line 17: / Line 37: @@
 [[Category:Microsoft]]
 [[Category:MS-DOS]]
 [[Category:File formats with too many extensions]]

← Older revision		Revision as of 00:31, 15 June 2024
Line 6:		Line 6:

	The developers of FreeDOS have attempted to reverse-engineer these formats to produce backup and restore commands in that system that are compatible with Microsoft's.		The developers of FreeDOS have attempted to reverse-engineer these formats to produce backup and restore commands in that system that are compatible with Microsoft's.
		+
		+	== Sample files ==
		+	* {{DexvertSamples\|archive/dosBackupFile}}

	== Links ==		== Links ==