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From: erice@microsoft.UUCP (Eric Evans)
Newsgroups: net.micro.pc
Subject: BACKUP file formats
Message-ID: <8735@microsoft.UUCP>
Date: Sun, 20-Jan-85 04:36:42 EST
Article-I.D.: microsof.8735
Posted: Sun Jan 20 04:36:42 1985
Date-Received: Fri, 25-Jan-85 06:42:13 EST
Organization: Microsoft Corporation
Lines: 59

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
 *
 *