   The program   FAILWRTA.COM   is a simple  short  TSR  which
hook the INT 24h DOS CRITICAL ERROR HANDLER.
   The reason  is  automatically  failing write protect errors
on  drive  A:.   Why?   Because  sometime  you can use a write
protect  diskette (to protect it against viruses or accidental
damages),  but  the program you start from A persists to write
something of not mandatory to the drive from which it started.
   If you can simply  fail  the write request (responding f to
the standard message "Abort, Retry, Ignore, Fail")FAILWRTA can
do this automatically for you.  (Obviously this is useful only
if failing the write request doesn't affect significantly pro-
gram's behaviour).
   The  little program is also an example of how it's possible
prevent  DOS from reinstalling default INT 24h handler without
transgress  to  IBM's  INTERRUPT-SHARING  PROTOCOL  (which TSR
producers should be encouraged to follow).
   The c program unifwrta.c (=uni(nstall) F(AIL)WRTA)  can  be
used to uninstall FAILWRTA.  It doesn't free memory allocated,
but it can be easily done;  I was  not  really  interested  to
uninstall failwrta for my goals, this could be  seen  only  as
an example of using IBM's I-S PROT. for uninstalling.  Freeing
FAILWRTA allocated memory is not so important, 'cause it  uses
only 400 bytes.
   Thanks a lot to Chris Dunford for posting  informations  on
IBM's INTERRUPT-SHARING PROTOCOL  and to Kris Heidenstrom  for
his useful help.

   The files here included can be freely distributed  provided
that they're distributed together, without stripping copyright
informations and without any change (I'd like to get blame for
my own errors and credit only where it is due - as Chris  Dun-
ford says).  Commercial use couldn't be done  without  contact
the author.

(c) 1996 by Luigi Mancinelli
E-Mail: manci@alpha.science.unitn.it
Post :
  Luigi Mancinelli 
  c/o Laboratori Didattici
  Facolt di Scienze
  Universit degli Studi di Trento
  38050 POVO-TRENTO (TN)
  ITALY
