1541 BAM AND VALIDATION TIPS
by Malcolm Cole, Memphis Commodore Users Club

 Have you ever lost a file from the directory, or for that matter the entire
directory???

 Well, before you get mad and throw that disk in the trash, listen to this!

 All is not lost.  Unless you have formatted the disk, all your programs are
still there!!! All you have to do is get the directory back...

 If you use disk doctor V4.0 (available in the club library) you can track
down that program and find out exactly where it was.

 First you need to view the bam, track 18 sector 0, and find out what tracks
and sectors are free. Next validate the disk and look at the disk.  All the
programs are still there!! View the bam again. Now you will notice there are
more tracks and sectors free.  This is where your program was or rather still
is. All you have to do is let the directory know.  Now comes the tricky part.

 Remembering that the 1541 writes files from track 17 out to 1 and track 19
out to 35, start at the first track/sector from 18 and trace the links through
until you come to the last block of data. This can be done with disk doctor by
starting at the first track and then hitting 'N' to link to the next block. If
it does not work the first time, just try another sector of the track. (The
more you try the better your success rate)  Be sure to keep track of the
number of blocks! Once you have this then go back to the first available entry
on the directory (Track 18 Sector 1,4,7,10,etc).

 Disk doctor will tell you where to put the name, link and block size. (The
link is the first two bytes of data before the program name). Simply hit '@'
and type in the track number, then do the same to the next byte which is the
sector number. Then move over to the name space, hit 'T' for text, and type in
the program name.  Be sure to hit return when finished. The next thing to do
is move over to the file size block, (about 10 spaces after the name). This is
a 2 byte field and if the program is over 256 blocks long (which I doubt) you
will have to use the second byte. Again, use the '@' key to enter the number
of blocks. You're almost done now, all that's left to do is rewrite the block
on the disk. This is done by hitting 'R' and 'Y'.

 Good luck, and let me know if you need any help with this.

 Malcolm Cole


 [Ed. Note:  Malcolm is a brand new member of MCUC.  Thank you Malcolm for
this excellent contribution to the newsletter.] 
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