modified buffer

[Doug Dodds <DODDS@TENEX.SCRC.Symbolics.COM>]

    Date: Fri, 26 Jul 85 21:26 CDT
    From: David Vinayak Wallace <Gumby@MCC-AI>

    In Symbolics 3640 Zwei in Release 6.0, MCC-Site 6.0, IP-TCP 29.0,
    microcode TMC5-IO4-ST506-MIC 319, on Lord Ganesh:

    1> Why do commands like c-X c-O set the modified bit even if they don't
       change the buffer?

c-X c-O doesn't in the development system, and never did, as far as I
can remember.  In what circumstances did this happen to you, for which
commands?

    2> Why can't I reset the unmodified bit on buffers which aren't
       associated with files?

Hmm, too many multiple negatives here; I take it you are asking why you
can't remove the "modified" mark on non-file buffers, i.e., make the "+"
disappear from that buffer's line in the Edit Buffers listing.

The immediate answer is that they aren't set up to have that done.  File
buffers have a Tick and a Save-tick.  The modified quality is set in
them by setting the Save-tick to the current tick, making it greater
than Tick.  

Non-file buffers are not associated with a file, and are of a different
flavor, which doesn't have a Save-tick and Read-tick.  There is no "*"
shown in the mode line for them.  The "+" in the Edit Buffers listing
reflects, I think, whether the interval has been munged or not.  I agree
that it's sort of inconsistent with the appearance and user operations
of file buffers.

As to why it is implemented that way, I don't know what policy, if any,
directed this.  Perhaps an older hand can comment on this.  It would be
easy to change the way "modification" is handled in non-file buffers,
but it should be done with an overall plan, and to improve consistency.
We'll collect comments on this for a future enhancement.