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The IBM 701, known as the Defense Calculator while in development, was announced to the public on April 29, 1952, and was IBM’s first commercial scientific computer•. Its business computer siblings were the IBM 702 and IBM 650. The system used electrostatic storage, consisting of 72 Williams tubes with a capacity of 1024 bits each, giving a total memory of 2048 words of 36 bits each. Each of the 72 Williams tubes was three inches in diameter. Memory could be expanded to a maximum of 4096 words of 36 bits by the addition of a second set of 72 Williams tubes or by replacing the entire memory with magnetic core memory. The tube memory access time was 30 microseconds. The core memory access time was 18 microseconds. A whole word addition operation took 5 – 12 microsecond machine cycles (60 microseconds), multiply and divide operations each took 38 – 12 microsecond machine cycles (456 microseconds). Instructions were 18 bits long, single address. Numbers were either 36 bits or 18 bits long, signed magnitude, fixed point. The IBM 701 had only 2 programmer accessible registers: The IBM 701 system was composed of the following units: Nineteen IBM 701 systems were installed *. The University of California at Livermore developed a language compilation and runtime system called the KOMPILER for their 701. A Fortran compiler was not released by IBM until the IBM 704. The successor of the 701 was the index register-equipped IBM 704, introduced 4 years after the 701. The 704 was not compatible with the 701, however, as the 704 increased the size of instructions from 18 bits to 36 bits to support the extra features.
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