Past forward: programming with plugs and cords

In 1950, physicist Arnold Nordsieck built this analog computer from US $700 worth of surplus parts. To program the machine, which solved differential equations, you plugged in the tangle of cords in specific patterns. Caution was advised. "Once one end of a cord is plugged in, the prongs of the free plug may have up to 105 volts of potential difference between them," Nordsieck noted in a memo. "Hence the operator should hold the live plug in such a way that the prongs do not touch him or anyone else or any metal." For more on Nordsieck's differential analyzer, go to http://spectrum. ieee.org/pastforward1217