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Unformatted text preview: Proof method: construction October 5, 2005 6 Equivalent machines M 0 1 ~ ~ ~ ~ ~ ~ a a a ~ ~ ~ ~ ~ a b ~ ~ ~ ~ ~ ~ # 1 # a a a # a b # ~ ~ S October 5, 2005 7 Simulating ktape behavior • Single tape start string is #w#~ #...#~ # • Each move proceeds as follows: – Start at leftmost slot – Scan right to (k+1) st # to find symbol at each virtual tape head – Make second pass making updates indicated by ktape transition function – When a virtual head moves onto a #, shift string to right October 5, 2005 8 Corollary Corollary: A language is Turingrecognizable if and only if some multitape Turing machine recognizes it. October 5, 2005 9 Example • Using 2tape Turing machine, write a copy machine • Copy tape 1 to tape 2 • Move tape 1 to beginning • Copy tape 1 to tape 2 • Accept...
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 Spring '11
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 Transition function, multitape Turing machines

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