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Combination:Calculating Machine and Printer, 1897

Building the Machine

Burroughs exercised extreme caution while drawing out the plans for his adding machine. Still troubled by the amount of time he wasted as a result of errors, he was determined that his adding machine be as fool-proof as possible. So preoccupied with perfection was he that he engraved his master drawings onto copper plates under a magnifier. Burroughs’ quest to eradicate error is seen in the design he chose for the keyboard of his adding machine. He settled on a nine-column structure, allotting a separate column of keys for every decimal place.

Despite the possibility of a “ten-key” keyboard design, which would allow the place to shift automatically, Burroughs opted for his “full” keyboard model. He reasoned that such an arrangement would lessen the chance of the operator of the machine pressing a key twice, or not pressing down hard enough, and throwing off the whole calculation. He therefore installed a nine-column keyboard, each column being made up of nine keys representing digits one through nine.

Burroughs incorporated other safeguards into his design. He equipped the mechanism with a “locked keyboard,” which caused it to freeze if there was an attempt made to punch two keys in the same column. Furthermore, when a key was pressed down, it stayed down. This enabled the operator to verify the sum he had entered before pulling the handle on the side of the machine and entering that sum into the numerical index. Finally, the machine had the capacity to print, so as to prevent discrepancies between the correct sum and the number copied down by the clerk or bookkeeper operating the machine.