On 3/26/17, Dave Horsfall <dave(a)horsfall.org> wrote [regarding the PDP-8]:
Yep, it could add, but not subtract. Dammit, but
I'm trying to think of
the CADET acronym; it went something like "Can't Add, Didn't Even
Try".
CADET was the official IBM internal development code name for the
1620, designed to be a low cost computer for the scientific
marketplace. Part of the reduced cost was attained by abandoning the
traditional ALU circuitry. Instead the 1620 did arithmetic by table
lookup. The joke was made that CADET stood for "Can't Add, Doesn't
Even Try", and that interpretation stuck and became popular with the
machine's user community.
-Paul W.