Computer Science 383

Theory of Computer Science

Fall 2017



Bob Geitz, King 223A


Office Hours:

MWF 1-3, Thursday 10-12, or by appointment

I am around most of the day when I am not in class.


This is a course in the theory of computation, a field that is considerably older than computers and computer science itself. We will look at issues related to what can be algorithmically computed and what can be said about the compuational process, including time and space complexity. Although the models of computation we will use are quite concrete and easily programmed, our interest in them is primarily mathematical. We will write many proofs, just as you did in the Algorithms class, but the proofs in this class tend to be more constructive and less abstract.


Automata Theory, Languages, and Computation, 3rd edition by Hopcroft, Motwani, and Ullman; Pearson/Addison-Wesley 2007. I am sorry this is expensive, but I think it is the clearest book available on the theory of computation.

Exams and Grading:

We will have 2 in-class exams during the semestezr and a comprehensive final exam. Here is how the grades for the course will be composed:

Note that the final exam will be Wednesday, December 13 at 9AM. This time is set by the Registrar and I cannot change it for the class or for individuals. If you have issues with this time you should talk to the Dean of Studies immediately.


Most of your learning in the course will come from the homework. The homework assignments will take time -- I would guess about 6 to 10 hours per week. You are welcome, and even encouraged, to form a study group to work on the homework. Mathematics is all about communication. The most important thing you can take from this course is the ability to formulate a convincing mathematical proof and that requires an audience to be convinced. So you can work out solutions to the problems in a group. However, you must write up your own statement of the solutions.

Your solutions shoould be submitted as a hard copy; I will not accept homework by email.. Many proofs in this class consist of diagrams, and those can be hand-drawn as long as they are legible. Narrative proofs should be typed. I don't particularly care if you use TeX or MS Word, but I want printed, not handwritten text. There is a reason for requiring you to type solutions. We are all sloppy with hand-written copy; we cross things out, draw arrows to new text, and so forth. Mathematics requires precision and careful use of language. It is much easier to see if a proof is correct if it is typed.

At the top of your solutions say who you worked with on the assignment. If you worked with person X and your solution isn't quite clear, person X's solution might help us to understand yours. Somewhere, preferably at the end, include the Honor Pledge: "I have written these solutions myself; I have given them to no one else"

Late homework: You can hand in one assignment up to 2 days late without penalty. Other assignments can be handed in up to 2 days late but are docked 50%. Except in extreme circumstances (I would need to hear from your class dean) homework that is more than 2 days late will receive no credit. For the most part you are better off turning in an assignment that is incomplete than turning it in late.


The Honor Code

The Honor Code has a straightforward application to this class. On all of the exams you are responsible for your own work; you may neither give nor receive any information during the course of the exam. If someone takes an exam at a different time than the rest of the class there may be no communication concerning the exam between that person and anyone else in the class, not even whether the exam was easy or difficult. For the homewok you are welcome to talk to anyone you like but you must write your own solutions.

Course outline:

Week Day Topic Notes
Week 1

Aug 28-Sept 1


Finite Automata; Regular Languages

Chapters 1,2
Week 2 Sept 6-8

Regular Expressions.

The equivalence of Regular Expressions and Finite Automata

Chapter 3
Week 3 Sept 11-15

The Pumping Lemma

Determining whether a language is regular

Chapter 4
Week 4 Sept 18-20

Propeties of Regular Languages

Chapter 4

No class on Friday Sept 22

Week 5 Sept 25-29 Context-Free Grammars and Languages

Chapter 5

Exam I: Reular Languages

Week 6 Oct 2-6 Pushdown Automata
Chaptper 6
Week 7 Oct 9-13 Context-Free Languages and Pushdown Automata Chapter 7
Week 8 Oct 23-27 Properties of Context-Free Languages hapter 7
Week 9 Oct 30-Nov 3 Turing Machines and Computability

Chapter 8


Week 10 Nov 6-10 Other Models of Computation

Chapter 9

Exam 2: Context-Free Languages

Week 11 Nov 13-17 The Halting Problem and Other Undecidable Problems

Chapter 9


Week 12 Nov 20-22

NP Completeness

Chapter 10
Week 13 Nov 27-Dec 1 Cook's Theorem Chapter 10
Week 13 Dec 4-Dec 8 Other "Impossible" results


Final Exam: Wednesday, December 13, 9AM