First shown at Chicago CES in January 1977, the Commodore PET was the first true appliance personal computer - one which could be taken out of the box, plugged in and used straight away. It evolved from MOS Technology's KIM-1 single-board computer, which had been launched in 1976, and was pretty much a KIM-1 with more memory, a keyboard and a monitor, in a metal case.

It was also known as one of the "1977 Trinity", along with the Apple II and the TRS-80 which were released within a few months of each other. Of the three, both the Apple and the TRS-80 were actually commercially available before the PET, with the TRS-80 being the run-away best seller for the first couple of years.

The PET was especially popular in education and laboratory settings, thanks to its rugged construction, and sold particularly well in Europe.