IBM 601

The tabulators that built IBM's first thirty years could add and subtract, which was quite enough to total a census or a payroll. Multiplication had to be done by hand or on a desk calculator, which shut the equipment out of engineering and science entirely. The IBM 601 fixed that: it read two numbers from a card, multiplied them in a relay unit, and punched the product back into blank columns on the same card. One card in, one answer out, at roughly a card per second.

About fifteen hundred were built through the 1940s, and they landed where you would expect — actuarial work, astronomical tables, ballistics. Wallace Eckert built his computing laboratory at Columbia around machines of this kind and demonstrated that a room of card equipment could be driven as a single calculating instrument. The 602, 603 and 604 carried it further; the 604 of 1948 replaced the relays with vacuum tubes and put the program on a plugboard.