In the early 1940s the earliest electronic digital computers were born. In this photo (taken in 2002 at the Computer Museum in Mountain View, California) Jef stands alongside one of the racks from the earliest Eniac.
Jef was born about the same time that this first Eniac was, which is why they get along so well together. Jef's first programming experience was with the Merlin computer at Brookhaven National Laboratory on Long Island in New York in the late 1950s. It looked much the same as the Eniac.