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IBM 701

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.

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. Memory could be expanded to a maximum of 4096 words of 36 bits by the addition of a 2nd set of 72 Williams tubes or by replacing the entire memory with magnetic core memory. The tube memory access time was 30μs. The core memory access time was 18μs.

Instructions were 18 bits long, single address.

Numbers were either 36 bits or 18 bits long.

The IBM 701 had only 2 programmer accessible registers:

  1. The accumulator was 38 bits long (adding 2 overflow bits).
  2. The multiplier/quotient was 36 bits long.

The IBM 701 system was composed of the following units: Nineteen IBM 701 systems were installed [1].

The successor of the 701 was the index register-equipped IBM 704, introduced 4 years after the 701.

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