A computer made By IBM oriented toward scientific work. The 709 had the same Basic architecture as the IBM 704But with many I/O and performance refinements over the 704. The IBM 709 (like the 704) had 36-Bit memory words, 15-Bit addresses and instructions with one address. A few {index register} instructions had the infamous 15-Bit decrement field in addition to the 15-Bit address. The IBM 7090 was a transistorised version of the 709. [Difference Between 704 and 709?] (1999-01-19)