THIS PAGE IS BLANK NEW AGE INTERNATIONAL (P) LIMITED, PUBLISHERS New Delhi · Bangalore · Chennai · Cochin · Guwahati · Hyderabad Jalandhar · Kolkata · Lucknow · Mumbai · Ranchi PUBLISHING FOR ONE WORLD Visit us at www.newagepublishers.com Copyright © 2005 New Age International (P) Ltd., Publishers Published by New Age International (P) Ltd., Publishers All rights reserved. No part of this ebook may be reproduced in any form, by photostat, microfilm, xerography, or any other means, or incorporated into any information retrieval system, electronic or mechanical, without the written permission of the publisher. All inquiries should be emailed to [email protected] ISBN (10) : 81-224-2294-2 ISBN (13) : 978-81-224-2294-8 PUBLISHING FOR ONE WORLD NEW AGE INTERNATIONAL (P) LIMITED, PUBLISHERS 4835/24, Ansari Road, Daryaganj, New Delhi - 110002 Visit us at www.newagepublishers.com (cid:1)(cid:2)(cid:3)(cid:4)(cid:5)(cid:6)(cid:3) To understand the fundamentals of computer science it is essential for us to begin with study of the related mathematical topics ranging from discrete mathematics, concepts of automata theory and formal languages. It is high time to recognize the importance of discrete mathematics as it finds various applications in the field of computer science. However, it requires a full fledged study and its potential with respect to computer sciences and natural sciences have long been well recognized. To understand the principles of computer science that is evenly acknowledged as mathematical foundation of computer science, this book present a selection of topics both from discrete mathematics and from automata theory and formal languages. The objective of selection of topics was due to my aspiration to commence with most of the fundamental termi- nology employed in higher courses in computer science as plausible. As per the requirements of the study, the formal appearance of the discrete mathematics includes set theory, algebraic systems, combinatorics, Boolean algebra, propositional logic, and other relevant issues. Like- wise, abstract models of computations, models of computability, language theory concepts, and the application of language theory ideas are the subject matter of the concepts of automata and formal languages. These topics will also assist to understand the concepts and philosophies used in advanced stages of computer learning such as computation theory and computability, artificial intelligence, switching theory and logic design, design of softwares like high speed compilers, sophisticated text processors and programming languages, assembly and rescue of information. The texts of this book are intended primarily for use in graduate as well as post graduate courses in ‘Mathematical Foundation of Computer Science’, ‘Discrete Mathematics’ and ‘Automata Theory and Formal Languages’. Although, the topics discussed in the book primarily focuses on the mathematical aspects of engineering in context of computer science, however it is also suited to the technical professionals. dharm d:\N-com\TITLE.pm5 iv ( vi ) (cid:7)(cid:8)(cid:9)(cid:10)(cid:11)(cid:5)(cid:9)(cid:10)(cid:8)(cid:12) The manuscript presented in this book is an outcome of the experience gained in the teaching the courses like discrete mathematics, automata theory, and mathematical foundation of com- puter science at Department of Computer Science & Engineering at I E T, UP Technical Uni- versity, Lucknow and elsewhere for last ten years. I am hopeful that presentation of this text imitates the planning of the lectures. I always tried to avoid the mathematical-rigors, compli- cated concepts and formalisms and presented them in a more precise and interesting manner. Moreover, I hope during my teaching students not only learned the courses as a powerful math- ematical tool but also widened their ability and understanding to perceive, devise, and attempt the mathematical problems with the application of the theory to computer science. The prolific and valuable feedback from my students motivates me to prepare this manuscript. Ultimately, I expect that this text would extend the understanding of mathematical theory of computer science with the explosion of computer science, computer application, engineering, and infor- mation technology. dharm d:\N-com\TITLE.pm5 v (cid:4)(cid:3)(cid:5)(cid:9)(cid:13)(cid:2)(cid:3)(cid:14)(cid:8)(cid:4)(cid:14)(cid:9)(cid:15)(cid:3)(cid:14)(cid:16)(cid:8)(cid:8)(cid:17) The interesting feature of this book is its organization and structure. That consists of systematizing of the definitions, methods, and results that something resembling a theory. Simplicity, clarity, and precision of mathematical language makes theoretical topics more appealing to the readers who are of mathematical or non-mathematical background. For quick references and immediate attentions—concepts and definitions, methods and theorems, and key notes are presented through highlighted points from beginning to end. Whenever, necessary and probable a visual approach of presentation is used. The amalgamation of text and figures make mathematical rigors easier to understand. Each chapter begins with the detailed contents which are discussed inside the chapter and conclude with a summary of the material covered in the chapter. Summary provides a brief overview of all the topics covered in the chapter. To demonstrate the principles better, the applicability of the concepts discussed in each topic are illustrated by several examples followed by the practice sets or exercises. The material of this book is divided into 5 Units that are distributed among 12 chapters. Unit I gives general overview of discrete objects theory its relations and functions, enu- meration, recurrence relations and algebraic structures. It contains four chapters. Chapter 1 is a discussion of discrete objects theory its relations and functions. We start our discussion from the theory of discrete objects which is commonly known as algebra of sets. The concepts of relations and functions are presented after a discussion of algebra of sets. This chapter is concluded with the study of natural numbers, Peano axioms and mathematical in- duction. Chapter 2 discusses enumeration that includes discrete numeric functions and generat- ing functions. This chapter covers a class of functions whose domain is the set of natural num- bers and the range is the set of real numbers—better known as discrete numeric functions that are widely used in digital computations. An alternative way to represent the numeric functions efficiently and conveniently the reader will also find a discussion over generating function in the chapter. Chapter 3 is concerned with recurrence relation and the methods of finding the solution of the recurrence relation (difference equation). A variety of common recurrences obtained from the algorithms like divide & conquer and chip & conquer is given. The chapter concludes the methods to obtain the solution of the recursive procedure codes. Chapter 4 Latter in this unit we emphasized the algebraic structures where a thorough discussion of group theory and brief discussion of other algebraic structures like rings and fields are presented. This discussion is in fact very important in formal language theory and automata. This chapter concludes with the discussion of class of group mappings like homomorphism, isomorphism, and automorphism. Unit II is devoted to the discussion of propositional logic and lattices that are presented in two chapters. Oaf! After a successful study of mathematical–rigors, readers find an interesting and detail overview of logic in Chapter 5. An elementary introduction to logic not only enlightens dharm d:\N-com\TITLE.pm5 vi ( viii ) the students who are eager to know the role of logic in computer science but equally to other students of human sciences, philosophy, reasoning, and social sciences as well. A brief discus- sion of the theory of inference persuades the criteria to investigate the validity of an argument is included. In the chapter the stress is mainly on the natural deduction methods to investigate the validity of an argument instead a lengthy and tedious approach using truth table. Further- more, the introduction of predicate logic and inference theory of predicate logic along with a number of solved examples conclude the chapter. Chapter 6 deals the Order Theory that includes partial ordered sets (posets) and lat- tices. This chapter also covers a detail discussion on lattice properties and its classification along with a number of solved examples. Unit III, IV, and V are concerned with automata theory and introduction to formal languages, which comprises chapters 7, 8–9, and 10–12 correspondingly. Chapter 7 starts with the study of introduction to the languages and finite automata. The class of finite automata- deterministic and nondeterministic is included with the definition, representation, and the discussion of the power of them. Chapter 8 deals the relationship between the classes of finite automata. Examples are given to explain better how one form of finite automata is converted to other form of automata with preservance of power. Of course, a brief illustration of the state minimization problem of deterministic finite automata concludes the chapter. Chapter 9 discusses about the regular expressions. Since generalization of regular expression gives regular language which is the language of the finite automaton. So this chapter illustrates the relationship between finite automata and regular expressions and vice-versa. This chapter also introduces another form of finite automata called finite automata with output such as Melay and Moore machines, which operate on input string and returns some output string. It also included the discussion on equivalence of Melay and Moore machines. Chapter 10 deals with regular and non-regular languages. To prove whether any lan- guage is regular or not we discuss a lemma called pumping lemma of regular language. This lemma is necessarily checking the regularity of the language. The characterizations of regular languages and decision problems of regular languages are also discussed here. Chapter 11 begins with the study of grammars. Classification of grammars of type 0, type 1, type 2, and type 3 are discussed here. A detailed discussion of non-regular grammar such as context free grammar (type 2) and context free language its characteristics, ambiguity features are presented in this chapter. The automaton which accepts the context free language is called pushdown automata. This chapter also discusses about the pushdown automata. Reader will also find the simplification method of any grammar including normal forms of grammars. Pumping lemma for proving any language is context free language or not and a brief discussion on decision problems concludes the chapter. Chapter 12 deals the study of an abstract machine introduced by Allen Turing called Turing machine. Turing machine is a more general model of computation in such a way that any algorithmic procedure that can be carried by human could be possible by a Turing machine. Chapter includes a brief discussion on this hypothesis usually referred as Church-Turing hypothesis which laid the theoretical foundation for the modern computer. Variations of Turing machines and its computing power concluded the study of this chapter. In Appendix a discussion on Boolean algebra, where reader will find the basic theorems of Boolean algebra and its most common postulates. A preamble to Boolean function, simplifica- tion of Boolean function and its application in the logic deign of digital computers is presented at last. dharm d:\N-com\TITLE.pm5 vii (cid:5)(cid:9)(cid:9)(cid:3)(cid:12)(cid:9)(cid:10)(cid:8)(cid:12)(cid:18) Even after immense forethoughts a book covering this variety of text it is probable to contain errors and lapses. I would appreciate you if you find any mistakes or have any constructive suggestions it will be my pleasure to look into your suggestions. You can mail your comments to Mathematical Foundation to Computer Science—Y N Singh Department of Computer Science & Engineering Institute of Engineering & Technology, UP Technical University, Lucknow-226 021 Alternatively you can use e-mail [email protected] to submit errors, lapses and constructive suggestions. (cid:5)(cid:6)(cid:17)(cid:12)(cid:8)(cid:19)(cid:20)(cid:3)(cid:21)(cid:22)(cid:3)(cid:7)(cid:3)(cid:12)(cid:9)(cid:18) I owe my deep concerns to many individuals whose encouragements, guidance, and suggestions have resulted in a better manuscript: Prof D S Chauhan Hon’ ble Vice Chancellor, UP Technical University, Lucknow Prof V K Jain (Ex.) Director & Head, Deptt. of CSE, HBTI, Kanpur Prof L S Yadav Director, IET, Lucknow Prof S N Singh Deptt. of Electrical Engineering, IIT, Kanpur Prof S K Bajpai Head, Deptt. of Computer Sc., IET, Lucknow Prof N P Padhey Deptt. of Computer Sc., IIT, Roorkee Prof B N Misra Coordinator Deptt. of Biotechnology, IET, Lucknow Prof V K Singh Examination Controller & Head Deptt. of Applied Science, IET, Lucknow Additionally I thank to my colleagues’ faculty members and friends. My special thanks go to the students in Mathematical foundation of computer science & automata theory classes who provided me valuable feedback and critical appraisal. I experience a pleasure working with New Age International Press. Every one contrib- uted immensely to the quality of the final manuscript. I specially thanks to L N Misra for his encouragement, support and assistance. Finally I pay my gratitude to the family members Saraswati (wife), Siddhartha (son), Divyanshi & Lavantika (daughters) for their love and patience during writing this book. At this moment, I can’t forget to memorize my late father B R Singh Rajput and my late teacher Dr Srikant Srivastawa who has been my hub of inspiration. I affectionately dedicate this book to all of them. I E T, Lucknow Y N Singh dharm d:\N-com\TITLE.pm5 viii