CPSC 421 501 Midterm on Wednesday Oct 30

Some study materials are availableonline

Hw 6 Not collected solutions willbe up on Oct 23

M w f

latter s classMostof 128C 30 take questiontheclasswe willtakequestion

Exam coverage is on websiteHandout on countabilityetcCh l Sip i Added Myhill Merode

Omitted 1.4 PumpingLemm

ch 3 Sip 3,1 Turing machines

Only ask forna

T m construction far regular language

3,3 HilbertiprtensDescriptions of

G p T.vn'smyD

M wdescriptionofTuringmachine 1input

DFA TuringmachinePhase1 blahphase 2

then implement

NFA phases 90 E 9

a 0,1 VIC I

9rej Utvsometimesfqz u u

gaa u V

might be easier to writethatI0,0

Gaao

o are10

Universal Turing machines

M Turing machine w input to M

insist state L's SE size ofM I gf I E I f gives statetapesymbolLK

nlt Nh M M S 397 Rthen

m w 23 3 400 84,1i 84,2

Q 1,2 23iconvention Einit

q V

input I 2 2 2 22 2 2 3

long word our 0 ya L R

Claim There is a universal Turning mode i.e

on input M w we end on face if Macceptow

Grej rejects w

never half i il neverloopy halts a w

Rene There isn't a universal DFI Comparison

Il l l l I i N FA

Claim Acceptm Aim M w

maggerts

is recognizable but undecidable

Same Haltym M wM acepts W or

M rejects w

Decidable M decides a language L over Efor we W EL M accepts wal j WH L M rejects w

Recognizable Any Turing machine M with input alphabet E

recognizes Ls WE E M accepts w

It doesn't include WE sit M rejects or loops on w

QampkiAumversdturihgmachmerATM.proSo Atm is recognizable by a Turing machine a universal

Clem's Atm is not decidable

Preet Say that H decides Atm Then build anotherT.vn on input 5 see if

of a valid Tur machis the description D

mif so feed LD LD to Hif H accepts DLD we reject Dif H rejects D LD we accept D

Yha happens to M en input LMLast Complement of Atm ATM is not recognisable