Discovery of the missing sequence-controlled relay calculator Zuse M9

Abstract

In 2010 Germany and Switzerland celebrated the 100th birthday of the great computer pioneer Konrad Zuse, inventor of world’s first program-controlled binary relay calculator using floating-point arithmetic (Zuse Z3, 1941). In this connection we discovered a sequence-controlled relay calcula-tor, a calculating punch called M9, which has been missing for almost fifty years. This historical machine had been forgotten and was completely unknown even to historians of computing. How-ever, it is mentioned in Zuse’s memoir, but without a name. Several eyewitnesses are still alive. To our knowledge, only one device has survived. It is now conserved at the Museum für Kommu-nikation in Berne, Switzerland. Zuse KG had built some 20 to 30 M9s for Remington Rand, Zurich. The M9 was Zuse’s first relay calculator manufactured in series. Only two original machines of the first ten Zuse models still exist, the Z4 (Deutsches Museum, Munich) and M9 (=Z9, Museum für Kommunikation, Berne). Without renting Z4 to the Swiss Federal Institute of Technology (Zurich) for five years and the serial production of M9, Zuse KG would soon have disappeared from mar-ket-place.