Turing machine  n.  [After Alan M. Turing (1912-1954), British
mathematician and computer pioneer.] The earliest but still the fastest
and most reliable computing system ever conceived.  "Dis machine vill
run and run." --K. Goedel.

The Turing machine's legendary mean time between failure is best
exemplified by the absence of a power switch -- leading to the famous
Halting Problem.