Wilhelm Schickard was born in Herrenberg, Germany, in 1592, and became a renowned astronomer, mathematician, linguist, and Lutheran minister. He is credited with building in 1623 the world's first true mechanical calculator, his "calculating clock" (a somewhat misleading moniker, as the device did not tell time). Schickard's hand-powered calculator was quite sophisticated, especially considering that it was the first of its kind. It was about the size of a typewriter and could add, subtract, multiply, and divide. It operated on six-digit numbers and rang a bell to announce overflow (i.e., a calculation result too large to represent on its readout).

Calculating aids akin to the slide rule had been built before (e.g., Napier's rods), so what justifies calling Schickard's clock the first "true" calculator? In using Napier's rods and similar devices, the operator rotates marked cylinders or slides marked sticks past each other and...