Emacs c-X c-W doesn't increment the "number of writes to file" fdb halfword

[Chris Lindblad <CJL%MIT-OZ@MIT-MC.ARPA>]

    Date: Tuesday, 20 November 1984  19:56-EST
    From: Randy Haskins <rh at MIT-EECS>

									Actually,
    I'm not sure that it's the number of write count that matters, it's probably
    one of the bits in the backup word (like, "has this file been incrementally
    dumped?").  It's probably the fault of OPENF% or something like that, 
    though, not EMACS.

When dumper saves a file, it takes the left half of fbcnt (number of
writes to file) and stores it somewhere in the backup word in the fdb of
the saved file. When it is running an incremental save, it saves all
files that has the left half of fbcnt larger than the value in the
appropriate part of the backup word. If you modify a file, the left half
of fbcnt should be incremented. OPENF% normally increments this number
if a jfn is opened for write access. I don't know why, but when you c-x
c-w to an existing file, in EMACS, the left half of fbcnt is not
incremented. I suspect that EMACS is doing something tricky here, and is
screwing up. EMACS seems to be the only program that I have seen that
has this problem.