file: nov2.txt 
This week (week9) we take up Part TWO: Computability Theory.

In Sipser, Ch 3 - Church-Turing Thesis.

Section 3.1 - Turing Machines.
Section 3.2 - Variants of Turing Machines.
Secton 3.3 - The Definition of Algorithm.

The homework is Homework08.pdf with 2 problems on CFLs and 1 problem on TM.

We review the overview in Ch 0:

We are now doing Computability Theory. The classifiction of problems is by those that are solvable and those that are not.

In 1936, Alan Turing proposed a model called the Turing Machine.  It is similar to a finite automaton, but with unlimited and unrestricted memory.  It is a much more accurate model of a general purpose computer.

But there are some problems that Turing Machine cannot solve.  It might not halt, but just loop forever.