Columbia University Computing History

The IBM 405 Alphabetical Accounting Machine

IBM 405
The IBM 405 Alphabetical Accounting Machine. 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].

IBM 405
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!)."

Also see:

Commentary

I received the following email from "Strontium Black Cat" a.k.a. "Henry" in November 2018:

On your "The IBM 405 Alphabetical Accounting Machine" web page under the "Also see:" header it is stated that:

(Me again, Frank) Following up on this... THIS LINK (for as long as it lasts) takes you directly to the sequence of interest in Wing and a Prayer, and I took some screenshots:

Screenshot from Wing and Prayer
Receiving the message
Screenshot from Wing and Prayer
Taking it to the decoding room
Screenshot from Wing and Prayer
Punching the message onto cards
Screenshot from Wing and Prayer
The IBM 032 card punch
Screenshot from Wing and Prayer
The IBM 405
Screenshot from Wing and Prayer
Putting the cards into the 405 hopper
Screenshot from Wing and Prayer
IBM 405 type bars in action
Screenshot from Wing and Prayer
Printed page comes out
Screenshot from Wing and Prayer
Printing complete

Clearly neither the 032 nor the 405 could decrypt the message, so how does it come out of the 405 in clear text? What is not shown in film is that the 405 is merely the i/o device for an unseen top-secret IBM relay calculator that decrypts the message.

Frank da Cruz / fdc@columbia.edu / Columbia University Computing History / 2001 / Most recent update: 29 May 2019