September 28

September 28 - CSCI 2670 Introduction to Theory of...

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CSCI 2670 Introduction to Theory of Computing September 28, 2005
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September 28, 2005 Agenda • This week – Turing machines – Read section 3.1
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September 28, 2005 Announcements • Tests will be returned tomorrow • Tutorial sessions are suspended until further notice – Extended office hours while tutorials are suspended • Monday 11:00 – 12:00 • Tuesday 3:00 – 4:00 • Wednesday 3:00 – 5:00
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September 28, 2005 Recap to date • Finite automata (both deterministic and nondeterministic) machines accept regular languages – Weakness : no memory • Pushdown automata accept context- free grammars – Add memory in the form of a stack – Weakness : stack is restrictive
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September 28, 2005 Turing machines • Similar to a finite automaton – Unrestricted memory in the form of a tape •Can do anything a real computer can do! – Still cannot solve some problems • Church-Turing thesis : any effective computation can be carried out by
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September 28, 2005 Touring machine schematic Control a b a ~ • Initially tape contains the input string – Blanks everywhere else (denoted ~ in class … different symbol in book) • Machine may write information on the tape
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September 28, 2005 Touring machine schematic Control a b a ~ • Can move tape head to read information written to tape • Continues computing until output produced – Output values accept or reject
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September 28, 2005 Touring machine schematic Control a b a ~ • Turing machine results –Accept –Reject – Never halts • We may not be able to tell result by observation
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September 28, 2005 Differences between TM and FA
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This note was uploaded on 02/07/2011 for the course CS 501 taught by Professor Sm during the Spring '11 term at Indiana.

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September 28 - CSCI 2670 Introduction to Theory of...

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