Just as great oaks come from little acorns, so too do room-sized computers come from humble calculators. In the case of Fujitsu 's FACOM series of adding machines, that calculator grew into a computer that is the world's oldest still in use.

The FACOM - or Fujitsu Automatic COMputer - is in the news because the second of its kind, the 128B, is currently receiving a tune-up to give it a few more years' useful life. The company's goal is to push it to 2016, when it will complete 60 years of operation. To that end, retired FACOM experts are returning to Fujitsu to teach the firm's tyros how to make it tick.

The FACOM 128B, which covers 65 square metres of Fujitsu's factory floor, was developed in 1958, growing out of a bona fide calculator in the 128A. Unsurprisingly, the 128B's calculating speed is about as fast as a modern desktop calculator, a fact that underlines the talent of the engineers who used it to design Japan's first passenger plane, the YS-11. Let's see your Casio do that. J Mark Lytle