BACKUP
                        ------

         The concept behind "backup" is to use byte "t3" of the
         file name which, for those unfamiliar with the CP/M
         organisation is the third character in the "type"
         extension to the name.   For example, the name -

                   backup.c

         consists of -

                   name      ==>  "backup"
         and       type      ==>  "c" which, as you have already
         
         noticed doesn't contain 3 characters.   But not to worry,
         CP/M makes PROVISION for three characters which, if not
         actually used, are converted to spaces (ASCII 32, decimal).

         So, whether or not you choose to specify 3 characters in the
         extension, you always have 3 available to you and so we can
         set bit 7 in t3 (or un-set it) as we need to in the backup
         programme.   In fact this is what the programme does after
         it has archived (copied to the archive disk) the file(s)
         which haven't been previously archived by BACKUP.

         i.e. it then sets bit 7 of t3 to let BACKUP know that you
         have already archived this file.

         When you alter the file again, most text editors un-set the
         attribute bits in t1, t2 and t3 so that BACKUP will then
         regard the altered file as one which was not previously
         archived (which is true) and will archive it for you in the
         normal course of events.

         If YOUR text editor doesn't do this then use the companion
         programme SETATR ( set attributes) to make the edited file
         copyable, and BACKUP can then archive it for you.

         A couple of special point to be aware of when using BACKUP
         are -

         A.   It can be used to back-up a hard disk but, the first
              time you use it you should have previously used
              SETATR to make sure your normal "COM" files are not
              needlessly backed-up to the floppy disk.   You may
              also wish to disqualify all those other files which
              you already have 3 copies of, on floppy disk, and
              only archive the more recent work which you never
              seem to have the time to archive, usually.

         B.   Don't worry if you find you have filled the archive
              disk before archiving all the files on the master
              disk.   Just put another (clean, formatted) disk in
              the target drive, do a CONTROL-C, and re-run BACKUP.

              It won't re-copy the files it copied to the first disk
              but will start again from the file it wouldn't copy to
              the disk which became full, and copy the rest of the
              files to the new disk.

         C.   The normal usage of BACKUP is -

                        backup  d1  d2  <RETURN>

              where "d1" is the drive being copied and "d2" is the
              drive which contains the archive disk.   Either lower
              case or upper case is OK but note particularly that
              "d1:" is wrong.   Just enter the letter without the
              colon as BACKUP only expects a single character.

              If you don't remember this, or the order in which the
              transfer is made -

                        FROM  d1  TO  d2

              then just enter backup  <RETURN> and respond to the
              prompts which appear on the screen.

         D.   I didn't put in any special error handling functions
              to deal with the problem you will encounter when you
              try to back up a file which has been made R/O on the
              archive disk.   It was easy enough to remove the R/O
              status with the "set_bit" routine, and then erase the
              file on the archive disk before making the new copy
              with BACKUP.

              So beware, BACKUP will copy your files NO MATTER WHAT!


         That's about all there is to it.   BACKUP is a simple
         programme (which does a complex job) and I've kept it that
         way as I've seen a number of similar programmes in Public
         Domain software, but NONE of them worked when I tried them
         on my system!   Backup SHOULD work on any CP/M 2.2 system
         but if you have any problems send your bug reports to -

                             Phil Cogar,
                             P.O. Box 364,
                             Narrabeen,
                             N.S.W.   AUSTRALIA   2101
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