BACKUP (MS-DOS)
From Just Solve the File Format Problem
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{{FormatInfo | {{FormatInfo | ||
|subcat=Backup | |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 | + | 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 | + | There are at least two quite different formats: |
| + | * The format used by MS-DOS 2.0(?) through 3.2. We'll call it 2.0 format. | ||
| + | * The format used by MS-DOS 3.3 through 5.x. We'll call it 3.3 format. | ||
| + | |||
| + | For the format used by MS-DOS 6.x's MSBACKUP.EXE utility, see [[Norton Backup]]. | ||
| + | |||
| + | == 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. | ||
| + | |||
| + | An extra BACKUPID.@@@ file is written to each disk, containing general information about the backup. It doesn't contain any critical information. | ||
| + | |||
| + | === 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] | ||
| + | * One could presumably learn about the format(s) from the MS-DOS 4.0 source code, listed below. | ||
| + | |||
| + | == Software == | ||
| + | * [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 == | == Sample files == | ||
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== Links == | == Links == | ||
| − | |||
* [http://www.computerhope.com/backup.htm Backup command help] | * [http://www.computerhope.com/backup.htm Backup command help] | ||
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[[Category:Microsoft]] | [[Category:Microsoft]] | ||
[[Category:MS-DOS]] | [[Category:MS-DOS]] | ||
| + | [[Category:Multi-file formats]] | ||
[[Category:File formats with too many extensions]] | [[Category:File formats with too many extensions]] | ||
Revision as of 17:33, 4 July 2025
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.
There are at least two quite different formats:
- The format used by MS-DOS 2.0(?) through 3.2. We'll call it 2.0 format.
- The format used by MS-DOS 3.3 through 5.x. We'll call it 3.3 format.
For the format used by MS-DOS 6.x's MSBACKUP.EXE utility, see Norton Backup.
Contents |
Format details
Format details - 2.0
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.
An extra BACKUPID.@@@ file is written to each disk, containing general information about the backup. It doesn't contain any critical information.
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
- Tech docs from FreeDOS
- One could presumably learn about the format(s) from the MS-DOS 4.0 source code, listed below.
