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IBM 1620 Processor
1959
The processor of IBM's 1959 1620 (CADET), a decimal, variable-length scientific machine that added and multiplied by table look-up.
The 1620 has no arithmetic hardware at all: the Model 1 "Can't Add, Doesn't Even Try", performing addition through a table at storage locations 00300-00399 and multiplication through a table at 00100-00299. Data is a string of decimal digits, each with a flag bit that marks field boundaries and signs; instructions are a fixed twelve digits (a 2-digit op code and two 5-digit addresses).