Shift registers, as Leibniz had demonstrated 260 years earlier, could perform binary arithmetic simply by shifting an entire row of binary digits one position to the right or left. Data were never transferred directly between adjacent toggles; instead, the state of each individual toggle was replicated upward into a temporary register, the lower register was cleared, and then and only then were the data shifted, diagonally, back down into the original register. There was no lower bound to how slowly the computer could be stepped through a sequence of instructions. Unlike the well-behaved
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