the calculations. Surprised by market demand for it, IBM introduced in 1948 a more compact version, the 604, using 1250 miniature vacuum tubes in removable plug-in modules. Much faster than the 601, it could divide and perform up to 60 program steps in one card cycle. Some 5400 units were leased or sold, making it the first successful commercial application of electronic computation.

The Ferranti Mark 1 (1951) is considered the first commercial stored program vacuum