On Wed, Jan 11, 2017 at 10:07 AM, Noel Chiappa <jnc@mercury.lcs.mit.edu> wrote:

    > I wonder if >pdd ... was in any way any inspiration for /proc?

That may have been a bit too cryptic. "pdd" ('process directory directory')
was a top-level directory in the Multics filesystem which contained a
directory for each process active in the system; each directory contained data
(in segments - roughly, 'files', but Multics didn't have files because it was
a single-level store system) associated with the process, such as its kernel-
and user-mode (effectively - technically, ring-0 and ring-4) stacks, etc.

So if a process was sitting in a system call, you could go into the right
directory in >pdd and look at its kernel stack and see the sequence of
procedure calls (with arguments) that had led it to the point where it
blocked. Etc, etc.