Columbia University Computing History

The IBM 405 Alphabetical Accounting Machine

IBH 405
Photo: from Grosch [57] 1st Ed.

The IBM 405 Alphabetical Accounting Machine, 1934. This was IBM's high-end tabulator offering (and the first one to be called an Accounting Machine), complementing its numeric-only 285. The 405 was programmed by a removeable plugboard with over 1600 functionally significant "hubs", with access to up to 16 accumulators, the machine could tabulate at a rate of 150 cards per minute, or tabulate and print at 80 cpm. The print unit contained 88 type bars, the leftmost 43 for alphanumeric characters and the other 45 for digits only. The 405 was IBM's flagship product until after World War II (in which the 405 was used not only as a tabulator but also as the I/O device for top-secret relay calculators built by IBM for the US Army Signal Corps in 1943, used for decrypting German and Japanese coded messages [40]). In 1952, IBM first used core memory in an experimental 405 model [4].

Another view of the 405 from [4]; CLICK to enlarge.
  Herb Grosch recalls of his early days at Columbia University's Watson Lab [57]: "About equipment: after merging in the better machines from the [Astronomical Computing Bureau in the] Pupin attic (I kept the old 285 horizontal tabulator as long as Marjorie [Severy] had room for it, out of sheer wonder at its clumsiness), we had two machine rooms with sorters and reproducers and collators, an interpreter, a gang punch, and several key punches. The most expensive machine (renting for over $1000 a month with all the bells and whistles I could hang on it) was the huge 405 tabulator, with 80 characters of alphanumeric storage, eating and disgorging 150 80-character cards a minute, printing 80 characters wide a line at a time (the type bars were too long to do this at full speed, but other models could print numbers only, at 150 lines a minute or 200 digits a second; the earth shook!)."

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Last Update: Thu Aug 3 07:38:05 2017

Frank da Cruz / / Columbia University Computing History