Correct.  at was a v7-ism.   Trying to put a nicer face on the idea - that
is to say, I looked at the "at" command as a user-mode (command) front-end
to cron so you didn't have to edit the crontab yourself.  The later had
been around as a system support idea, since at least 6th edition - maybe
5th.

On Tue, Dec 8, 2020 at 1:51 PM Mary Ann Horton <mah@mhorton.net> wrote:

> My V6 manual has cron(VIII) - documentation of /usr/lib/crontab - but no
> mention of at.
>
> This is consistent with my recollection - I first saw at in V7.
>
>      Mary Ann
>
> On 12/8/20 10:11 AM, ron minnich wrote:
> > When I got into Unix in 1976 cron and at were both there.
> >
> > I got to wondering for no particular reason which came first -- I had
> > always assumed cron, but ...?
> >
> > Anyone know?
>