National
Semiconductor actually made calculators back in the 1970s - I
 used to have one maybe 20 years ago, but it is long gone. They also
 made a line of plug compatible S/370 mainframes, as well. 
 As well as watches and
video games.  I still have an NSC watch
 (nonfunctioning) and I recall giving a Pong game to my brother's
 family as a gift back then. 
 
    Chuck, you made me remember my first digital clock
    I was very young, about 4 or 5 years old (I'll be 35 in 3 days) and it
was a white plastic watch with a red face and very tiny red numbers that
lighted only with a press of a buttom. I remember clearly it was made by
texas instruments. I'd love to have one of these again, but I think with
this new wave of "everything vintage", it must be very expensive (and rare!)
these days... :o(
Stop the press!!! Here it is:
http://www.ledwatches.net/photo-pages/texas-instruments3.htm
I had the white one :o)