dave@zinfandel.UUCP (01/04/85)
< >
Sorry to bother the whole net (actually, you might be interested anyway), but
I could not get this message through the mail.
Date: 21 Dec 84 17:41:40 PST (Fri)
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Date: 21 Dec 84 17:41:40 PST (Fri)
From: ihnp4!zinfandel!dave (Dave Funk)
Subject: 1541 Scratch Proofing
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To: zehntel!ihnp4!cmcl2!acf4!per
About "scratch-proofing" files on the 1541....
Byte 2 (starting from byte 0) of the directory entry for a
given file contains the file type. This information is on
track 18, sector 0. To wit:
$80 DELeted
$81 SEQuential
$82 PRoGram
$83 USeR
$84 RELative
To scratch-proof a file, just change the '8' to a 'C'. This
sets bit six in byte number two. Now when you cat the disk,
you will see a '<' after the file type. If you try to scratch
it, you will not get an error, but the file is NOT actually
scratched. If you do another cat, it is still there just like
it always was. The only way to scratch it now is 1) reset bit
six or, 2) 'new' the disk. Pretty neat, huh?
Now, how does one do this? I suppose you could figure out a
way to send a command to the disk drive, but I just used a
disk editor. RUN magazine published one a few months ago --
I used CLONE (a commercial disk copier/editor).
If you need more details, just holler!
Dave Funk
Zehntel, Inc.
2625 Shadelands Drive
Walnut Creek, CA 92598
(415) 932-6900 x309
....!decvax!sytek!zehntel!dave
...."zehntel!dave"@BERKELEY