1948

IBM's first large-scale digital calculating machine, the Selective Sequence Electronic Calculator (SSEC), is announced. The SSEC is the first computer that can modify a stored program, and featured 12,000 vacuum tubes and 21,000 electromechanical relays.

IBM introduces the IBM 604 Electronic Calculating Punch. The mass-produced 604 features the industry's first assemblage of digital electronics replaceable as a unit. Service engineers can simply pull out a defective unit of the 604 and plug in a replacement, reducing downtime.