broehl@wateng.UUCP (Bernie Roehl) (01/10/85)
< crunch, crunch... >
Does anyone out there know the format of MS-DOS backup diskettes?
I've figured out the obvious stuff (i.e. that there's a file called
BACKUPID.@@@ on the disk, that that file's 128 bytes long and contains
some representation of the date, that the backup-up files have 128 bytes
set aside at the start (with the original path name starting at the fifth
byte), etc) but am looking for specifics.
I'd eventually like to be able to write a utility that let's me see the
original path names of backed-up files (easy) and let's me restore them
(trickier, especially since one file may be split across many diskettes).
Anyone out there at Microsoft able to provide any information? Thanks
in advance.
--
-Bernie Roehl (University of Waterloo)
...decvax!watmath!wateng!broehlerice@microsoft.UUCP (Eric Evans) (01/20/85)
Recently, some one wanted some information on the IBM/Microsoft hard disk BACKUP programs. I cannot send this directly to him because I lost his address. IBM chose the following formats for the BACKUPID.@@@ file and the header placed on each of the files which is backed up. They wrote the program BACKUP which is shipped with PCDOS. Microsoft has a compatible program which is being / will be shipped with MSDOS. Eric K. Evans decvax!microsof!erice * Each backup diskette contains the file BACKUPID.@@@. This file always * has the following format: * * BYTE | VALUE | USE * -------+-------+-------------------------------------------------- * 00 | 00/FF | not last/is last diskette * 01-02 | nn | diskette number in low byte, high byte, * | | decimal format (see NOTE 1) * 03-04 | nnnn | full year in low byte, high byte order * 05 | 1-31 | day of month * 06 | 1-12 | month of year * 07-0A | nnnn | standard MS-DOS time only if /T, 0 otherwise * 0B-7F | 00 | not used * | | * * * * * Each backup file has a 128 byte header on the front of it followed by the * true contents of the file: The header format is: * * BYTE | VALUE | USE * -------+-------+----------------------------------------------------- * 00 | 00/FF | not last/is last diskette on which this file resides * 01 | nn | diskette number * 02-04 | 00 | not used * 05-44 | nn | full filespec except for the drive designator * 45-52 | 00 | not used * 53 | nn | length of the filespec+1 * 54-7F | 00 | not used * | | * * * * *** NOTE 1 * * IBM uses 2 bytes in backupid.@@@ to store the backup diskette number. The * number is stored in a decimal, digit format in low byte, high byte order. * For example: * 1 is stored as 01 00 11 is stored as 01 01 * 9 is stored as 09 00 99 is stored as 09 09 * 10 is stored as 00 01 * *