packed permission bits in file systems?

[David Nicol]

On Thu, Jun 3, 2010 at 2:58 PM, Billy Crook <billycrook at gmail.com> wrote:
> Maybe David's thinking of a+x.  That would do what he's talking about.
>  I've never heard of 'packed permissions'.

I'm not thinking of a+x, I'm thinking of a file system so old that
saving six bits per file system entry was worth the resulting
confusion, like, PDP-10 or early seventies Unices.

a+ is probably the only time I ever encountered having one letter set
multiple bits, though.