[TUHS] Emacs and undump

[Lars Brinkhoff]

Johnny Billquist wrote:
> But having the memory around for a program, even if it is not running,
> is actually sometimes very useful. If ITS could handle that, while
> treating them as separate processes, all associated to one terminal,
> and let you select which one you were currently fooling around in,
> while the others stayed around, that is something I don't think I've
> seen elsewhere.

And it's not just a list structure, but a tree.  You can e.g. start a
new DDT, which itself can have inferior jobs (subprocesses).

To bring this slightly back on topic, ITS job handling was John Kulp's
inspiration for Unix job control.  Control-Z does pretty much the same
thing in both ITS and Unix.

> So, Emacs does it once, and then saves the state at the point where
> you can start editing.  But it does not mean that the memory is
> shareable. It's full of various data structures, and code, and that
> will change as you go along editing things as well.

Much is sharable.  There's a concept of purification (which also comes
from ITS).  A purecopy() function is used in temacs to put read-only
data in a special memory area.  That area will become sharable in the
dumped Emacs.