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[Outcomes Matrix]
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[Class Protocols]
[Exam Info]
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HW Assignments:
[Hw1] [Hw2] [Hw3]
[Hw4] [Hw5] [Quizzes]

Practice Exams:
[Midterm] [Final]

CS154 Spring 2020 Sec1 Home Page/Syllabus

Formal Languages and Computability

Instructor: Chris Pollett
Office: MH 214
Phone Number: (408) 924 5145
Office Hours: MW 1:30-2:45pm
(Via Zoom Meeting Until Further Notice)
Office Hours Zoom Meeting ID: 412-064-389
Meeting Password: 833994
Class Meets:
Sec1 MW 3:00-4:15pm in DH450
(Via Zoom Meeting Until Further Notice)
Class Zoom Meeting ID:828-646-949
Meeting Password: 216124


To take this class you must have taken:
Math 42
with a grade of C- or better.

Texts and Links

Required Texts: Introduction to the Theory of Computation. (3rd Ed.). Michael Sipser
Online References and Other Links: JFLAP.


From the catalog: This course covers the basics of finite automata, context-free languages, Turing machines, computability. Finite automata are used in the lexical analysis part of a compiler, and are also used for string matching, and for simple AIs in video games. Context-free languages are used for parsing in compilers. On the web, XML document type definitions allow one to specify a class of context-free languages. Computability is the study of what it is possibility to get a computer to do. In computability theory, we use an abstract model of a computer called a Turing Machine and study what it can and cannot do.

Course Learning Outcomes (CLOs)

By the end of this course, a student should be able to:

CLO1 -- Write a grammar for a language described otherwise.

CLO2 -- Construct deterministic and non-deterministic machines for various languages.

CLO3 -- Describe a language in terms of a regular expression.

CLO4 -- Find a regular expression for a language described by a finite automaton and conversely.

CLO5 -- Construct a deterministic finite automaton from a non-deterministic one.

CLO6 -- Minimize a deterministic automaton.

CLO7 -- Be able to use a pumping lemma to show that some languages are not regular and/or not context-free. Use closure properties to simplify proofs of non-regularity of languages.

CLO8 -- Be able to construct a pushdown automaton accepting a given language.

CLO9 -- Construct a Turing machine accepting some simple languages.

CLO10 -- State in precise mathematical terms what is meant by undecidability of the Halting Problem, and be able to show the undecidability of simple extensions of the Halting Problem, using the reduction technique.

Course Schedule

Below is a tentative time table for when we'll do things this quarter:

Week 1:Jan 27, Jan 29 Ch 0 Introduction to course, Sets, Relations, Functions
Week 2:Feb 3, Feb 5 Equivalence relations, Graphs, and Proofs
Week 3:Feb 10, Feb 12(Hw1) DFAs, Product Construction
Week 4:Feb 17, Feb 19 NFAs, Minimization
Week 5:Feb 24, Feb 26 Regular Expressions, Closure Properties of Regular Languages, Regular Grammars
Week 6:Mar 2, Mar 4 (Hw2 due Mar 6) More Closure Properties of Regular Languages, Pumping Lemma
Week 7:Mar 9, Mar 11(Midterm) Review
Week 8:Mar 16, Mar 18 Ambiguity, Chomsky Normal Form, CYK
Week 9:Mar 23, Mar 25 (Hw2 due Mar 26) Parsing CFGs, Greibach Normal Form, PDAs
Week 10:Mar 30, Apr 1 Spring Recess
Week 11:Apr 6, Apr 8 Pumping Lemma for CFLs, Compression, CFL algorithms, TMs
Week 12:Apr 13, Apr 15 Ch 5 Equivalence among machines models, UTMs, Diagonalization
Week 13:Apr 20, Apr 22 Read 6.1-6.2 Hierarchy Theorems, Complete Problems, Rice Theorem
Week 14:Apr 27, Apr 29 Read 6.3 Recursion Theorem
Week 15:May 4, May 6 Read 6.4 Komolgorov Complexity
Week 16:May 11(Hw5) Review
The final will be Wednesday, May 13 from 12:15pm-2:30pm


HWs and Quizzes 50%
Midterm 20%
Final 30%

Grades will be calculated in the following manner: The person or persons with the highest aggregate score will receive an A+. A score of 55 will be the cut-off for a C-. The region between this high and low score will be divided into eight equal-sized regions. From the top region to the low region, a score falling within a region receives the grade: A, A-, B+, B, B-, C+, C, C-. If the boundary between an A and an A- is 85, then the score 85 counts as an A-. Scores below 55 but above 50 receive the grade D. Those below 50 receive the grade F.

If you do better than an A- in this class and want me to write you a letter of recommendation, I will generally be willing provided you ask me within two years of taking my course. Be advised that I write better letters if I know you to some degree.

Course Requirements, Homework, Quiz Info, and In-class exercises

This semester we will have five homeworks, weekly quizzes, and weekly in-class exercises.

Every Monday this semester, except the first day of class, the Midterm Review Day, and holidays, there will be a quiz on the previous week's material. The answer to the quiz will either be multiple choice, true-false, or a simple numeric answer that does not require a calculator. Each quiz is worth a maximum of 1pt with no partial credit being given. Out of the total of twelve quizzes this semester, I will keep your ten best scores.

On Wednesday's, we will spend 15-20 minutes of class on an in-class exercise. You will be asked to post your solution to these exercises to the class discussion board. Doing so is worth 1 "pre-point" towards your grade. A "pre-point" can be used to get one missed point back on a midterm or final, up to half of that test's total score. For example, if you scored 0 on the midterm and have 10 pre-points, you can use your pre-points, so that your midterm score is a 10. On the other hand, if you score 18/20 on the midterm, you can use at most 1 pre-point since half of what you missed (2pts) on the midterm is 1pt.

Links to the current list of homeworks and quizzes can be found on the left hand side of the class homepage. After an assignment has been returned, a link to its solution (based on the best student solutions) will be placed off the assignment page. Material from assignments may appear on midterms and finals. For homeworks you are encouraged to work in groups of up to three people. Only one person out of this group needs to submit the homework assignment; however, the members of the group need to be clearly identified in all submitted files.

Homeworks for this class will be submitted and returned completely electronically. To submit an assignment click on the submit homework link for your section on the left hand side of the homepage and filling out the on-line form. Hardcopies or e-mail versions of your assignments will be rejected and not receive credit. Homeworks will always be due by midnight according to the departmental web server on the day their due. Late homeworks will not be accepted and missed quizzes cannot be made up; however, your lowest score amongst the five homeworks and your quiz total will be dropped.

When doing the programming part of an assignment please make sure to adhere to the specification given as closely as possible. Names of files should be as given, etc. Failure to follow the specification may result in your homework not being graded and you receiving a zero for your work.

Classroom Protocol

I will start lecturing close to the official start time for this class modulo getting tangled up in any audio/visual presentation tools I am using. Once I start lecturing, please refrain from talking to each other, answering your cell phone, etc. If something I am talking about is unclear to you, feel free to ask a question about it. Typically, on practice tests days, you will get to work in groups, and in so doing, turn your desks facing each other, etc. Please return your desks back to the way they were at the end of class. This class has an online class discussion board which can be used to post questions relating to the homework and tests. Please keep discussions on this board civil. This board will be moderated. Class and discussion board participation, although not a component of your grade, will be considered if you ask me to write you a letter of recommendation.


The midterm will be during class time on: Mar 11.

The final will be available on May 13 at 12:15pm. From then you will have until May 14, 11:59pm to submit your exam using the same mechanism as with the homework and midterm.

Originally, all exams for this class were to be closed book, closed notes and in this classroom. You were to be allowed only the test and your pen or pencil on your desk during these exams. Due to the cornonavirus the midterm was given online and was open book and note with a minimum 24 hours of allowed exam time. The final will also be online open book and note with a minimum 24 hour s of allowed exam time. The final will cover material from the whole semester although there will be an emphasis on material after the last midterm. No make ups will be given. The final exam may be scaled to replace a midterm grade if it was missed under provably legitimate circumstances. These exams will test whether or not you have mastered the material both presented in class or assigned as homework during the quarter. My exams usually consist of a series of essay style questions. I try to avoid making tricky problems. The week before each exam I will give out a list of problems representative of the level of difficulty of problems the student will be expected to answer on the exam. Any disputes concerning grades on exams should be directed to me, Professor Pollett.


If you believe an error was made in the grading of your program or exam, you may request in person a regrade from me, Professor Pollett, during my office hours. I do not accept e-mail requests for regrades. A request for a regrade must be made no more than a week after the homework or a midterm is returned. If you cannot find me before the end of the semester and you would like to request a regrade of your final, you may see me in person at the start of the immediately following semester.

University Policies and Procedures

Per University Policy S16-9, university-wide policy information relevant to all courses, such as student class time requirements expectations, academic integrity, accommodations, etc. will be available on Office of Graduate and Undergraduate Programs' Syllabus Information web page at Below are some brief comments on some of these policies as they pertain to this class.

Academic Integrity

For this class, you should obviously not cheat on tests. For homeworks, you should not discuss or share code or problem solutions between groups! At a minimum a 0 on the assignment or test will be given. A student caught using resources like Rent-a-coder will receive an F for the course. Faculty members are required to report all infractions to the Office of Student Conduct and Ethical Development.


If you need a classroom accommodation for this class, and have registered with the Accessible Education Center, please come see me earlier rather than later in the semester to give me a heads up on how to be of assistance.