I did a bit of searching on Google Books and there is an article from the June
28, 1972 issue of ComputerWorld that states "Ever since Hitachi introduce the
Hitac 10 as a 'personal computer' in 1969, not only the regular computer
manufacturers but electric appliance, calculator, watchmakers, communications
and software companies, and even textile manufacturers, have plunged into the
minigame." While they are talking about minis, what this does show is that the
term "personal computer" was used prior to the advent of the Altair.
