CIT 342: FORMAL LANGUAGES AND AUTOMATA THEORY NATIONAL OPEN UNIVERSITY OF NIGERIA FACULTY OF SCIENCE COURSE CODE: CIT 342 COURSE TITLE: Formal Languages and Automata Theory COURSE GUIDE CIT 342 Formal Languages and Automata Theory Course Developer Afolorunso, A. A. National Open University of Nigeria Lagos Course Co-ordinator Afolorunso, A. A. National Open University of Nigeria Lagos Course Editor Programme Leader Prof. Kehinde Obidairo NATIONAL OPEN UNIVERSITY OF NIGERIA National Open University of Nigeria Headquarters 14/16 Ahmadu Bello Way Victoria Island Lagos Abuja Annex 1 245 Samuel Adesujo Ademulegun Street Central Business District Opposite Arewa Suites Abuja e-mail: [email protected] URL: www.nou.edu.ng National Open University of Nigeria 2011 First Printed 2011 ISBN All Rights Reserved Printed by …………….. For National Open University of Nigeria TABLE OF CONTENTS PAGE Introduction............................................................... 3 What you will learn in this Course............................ 4 Course Aims.............................................................. 4 2 Course Objectives………………………………….. 4 Related Courses 5 Working through this Course..................................... 5 Course Materials......................................................... 5 Study Units ................................................................ 5-6 Textbooks and References ......................................... 6-9 Assignment File.......................................................... 10 Presentation Schedule................................................. 10 Assessment.................................................................. 10 Tutor Marked Assignments (TMAs) .......................... 11 Examination and Grading............................................ 11 Course Marking Scheme............................................. 12 Course Overview…………………………………… 12-13 How to Get the Best from This Course ...................... 13-15 Tutors and Tutorials ................................................... 15 Summary……………………………………............. 15 3 CIT 342 Formal Languages and Automata Theory Introduction CIT 342 – Formal Languages and Automata Theory is a two (2) credit unit course of 16 units. The course will cover the important formal languages in the Chomsky hierarchy -- the regular sets, the context-free languages, and the recursively enumerable sets -- as well as the formalisms that generate these languages and the machines that recognize them. The course will also introduce the basic concepts of computability and complexity theory by focusing on the question, "What are the fundamental capabilities and limitations of computers?" The concepts covered in this course will be amply illustrated by applications to current programming languages, algorithms, natural language processing, and hardware and software design. Also, in this course we shall investigate whether it is possible at all for a given language to find out if a given word belongs to it or not, and if it is possible how hard it will be. These constitute the fields of decidability theory and complexity theory, respectively. What we really want to do is to find out which problems can be solved in general, and for those problems that can be solved, how hard it is to solve them. In order to make these questions more precise, we encode problems as languages. Although the idea of automaton is quite old (for example a simple pendulum), it was Post's work, contemporary with Turing, that made possible a general characterization of machines that has been so helpful in the development of ideas ranging from combinational circuits to finite-state languages. Although not as powerful as the machines associated with Chomsky and Turing automata remain a very important tool in the elucidation of the inner workings of machines and provide an excellent starting point in understanding the basic ideas underlying contemporary science. It is a course for B. Sc. Computer science major students, and is normally taken in a student's third year. It should appeal to anyone who is interested in the design and implementation of programming languages. Anyone who does a substantial amount of programming should find the material valuable. This course is divided into four modules. The first module deals with the general concepts of formal languages The second module treats, extensively, regular languages and the class of automata, finite state automata, that recognises strings generated by regular grammar. The third module deals with context-free languages and pushdown automata The fourth module which is the concluding module of the course discusses Turing machines and the rest of the language classes 4 CIT 342 Formal Languages and Automata Theory This Course Guide gives you a brief overview of the course contents, course duration, and course materials. What you will learn in this course The main purpose of this course is to acquaint students with the fact that languages fall into various classes, according to their complexity. Some languages can be parsed, i.e. interpreted, by a very simple state machine. Others require the human brain, or something comparable. Languages also have many representations: machines that recognize them, expressions that describe them and grammars that generate them. Thus, we intend to achieve this through the following: Course Aims First, students will learn the key techniques in modern compiler construction, getting prepared for industry demands for compiler engineers. Second, students will understand the rationale of various computational methods and analysis. The third goal is to build the foundation for students to pursue the research in the areas of automata theory, formal languages, and computational power of machines Course Objectives Certain objectives have been set out to ensure that the course achieves its aims. Apart from the course objectives, every unit of this course has set objectives. In the course of the study, you will need to confirm, at the end of each unit, if you have met the objectives set at the beginning of each unit. Upon completing this course you should be able to: Discover computational thinking Understand the fundamental models of computation that underlie modern computer hardware, software, and programming languages. Discover that there are problems computer can solve. Discover that there are limits as to how fast a computer can solve a problem. Learning the foundations of automata theory, computability theory, and complexity theory. Learn about applications of theory to other areas of computer science such as algorithms, programming languages, compilers, natural language translation, operating systems, and software verification. Related Courses Prerequisites: CIT 331; Computer Science students only Working through This Course 5 CIT 342 Formal Languages and Automata Theory This course centres around three concepts: Languages, grammars, and automata. In order to have a thorough understanding of the course units, you will need to read and understand the contents, practise the steps by designing a compiler of your own for a known language, and be committed to learning and implementing your knowledge. You might need to listen to a short video cliques in some aspects of discussion for further explanation. For example, this 8 minutes video summarizes theory of computation. https://www.youtube.com/watch?v=dCiZZiqVv9w This course is designed to cover approximately seventeen weeks, and it will require your devoted attention. You should do the exercises in the Tutor-Marked Assignments and submit to your tutors. Course Materials These include: 1. Course Guide 2. Study Units 3. Recommended Texts 4. A file for your assignments and for records to monitor your progress. Study Units There are 16 study units in this course: Module 1: General Concepts Unit 1: Alphabets, Strings, and Representations Unit 2: Formal Grammars Unit 3: Formal Languages Unit 4: Automata Theory Module 2: Regular Languages Unit 1: Finite State Automata Unit 2: Regular Expressions Unit 3: Regular Grammars Unit 4: Closure Properties of Regular Languages Unit 5: The Pumping Lemma Module 3: Context-Free Languages Unit 1: Context-Free Grammars Unit 2: Properties of Context-Free Languages Unit 3: Pushdown Automata Unit 4: CFGs and PDAs Module 4: Turing Machines Unit 1: Turing Machines and the rest Unit 2: Turing Machines and Context-Sensitive Grammars Unit 3: Unrestricted Grammars Make use of the course materials, do the exercises to enhance your learning. Textbooks and References Alfred V. Aho, Monica S. Lam, Ravi Sethi and Jeffrey D. Ullmann (2007) Compilers Principles, Techniques, & Tools Second Edition Crespi R.S., Breveglieri L. and Morzenti A.(2019) Formal Languages and Compilation, Third Edition, Sprinwger, 2019. Daniel I.A. Cohen, ( ) Introduction to Computer Theory, John Wiley Publisher GeeksforGeeks (2020). Closure Properties of Regular Languages. Goswami D., Krishna K. V. (2010). Formal Languages and Automata Theory. Hopcroft H.E. and Ullman J. D. ―Introduction to Automata Theory Languages and Computation‖. Pearson Education John C Martin Introduction to languages and the Theory of Computation, John C Martin, TMH. Kamala K. & Rama R ( ) Introduction to Formal Languages , Automata Theory and Computation – Kavi M. ( ) Theory of Computation : A Problem – Solving Approach-, Wiley India Pvt. Ltd. Lewis H.P. & Papadimition C.H. ( ) Elements of Theory of Computation, Pearson /PHI Publisher Linz P. (2012) An Introduction to formal