On 09 Jul 2013, at 00:44, Jason Resch wrote:
Leibniz may have been the first computer scientist and information
theorist. Early in life, he documented the binary numeral system
(base 2), then revisited that system throughout his career. He
anticipated Lagrangian interpolation and algorithmic information
theory. His calculus ratiocinator anticipated aspects of the
universal Turing machine. In 1934, Norbert Wienerclaimed to have
found in Leibniz's writings a mention of the concept of feedback,
central to Wiener's later cybernetic theory.
In 1671, Leibniz began to invent a machine that could execute all
four arithmetical operations, gradually improving it over a number
of years. This "Stepped Reckoner" attracted fair attention and was
the basis of his election to the Royal Society in 1673. A number of
such machines were made during his years in Hanover, by a craftsman
working under Leibniz's supervision. It was not an unambiguous
success because it did not fully mechanize the operation of
carrying. Couturat reported finding an unpublished note by Leibniz,
dated 1674, describing a machine capable of performing some
algebraic operations. Leibniz also devised a (now reproduced)
cipher machine, recovered by Nicholas Rescher in 2010.
Leibniz was groping towards hardware and software concepts worked
out much later by Charles Babbage and Ada Lovelace. In 1679, while
mulling over his binary arithmetic, Leibniz imagined a machine in
which binary numbers were represented by marbles, governed by a
rudimentary sort of punched cards. 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.
Leibniz seems to have been very close indeed.
Thanks to a work by Jacques Lafitte(*), I tend to consider that
Babbage made the "full discovery" of the universal computer. "Full"
means that he discovered Church thesis. He discovered it when
realizing that the functional language that he invented to just
describe his machine was as much conceptually powerful than his machine.
To understand/discover Church thesis you have to discover two (rather
different) universal machines :)
(*) Lafitte, J. Réflexion sur la science des machines, Vrin, 1931.
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