 Modern electronic digital computers replace Leibniz's marbles moving by gravity with shift registers, voltage gradients, and pulses of electrons, but otherwise they run roughly as Leibniz envisioned in 1679.Later in Leibniz’s career (after the death of von Boyneburg), Leibniz moved to Paris and accepted a position as a librarian in the Hanoverian court of Johann Friedrich, Duke of Brunswick-Luneburg.Leibniz’s predecessor, Tobias Fleischer, had already created a cataloging system for the Duke’s library but it was a clumsy attempt.