Fundamentals of Programming Languages

449 Pages·1982·8.396 MB·

by  Ellis Horowitz (auth.)

FUNDAMENTALS OF
PROGRAMMING
LANGUAGES
Ellis Horowitz
Fundamentals of
Programming Languages
With 43 Figures and 34 Tables
Springer-Verlag
Berlin -Heidelberg New York 1983
Copyright © 1983 Computer Science Press
All rights reserved. No part of this work may be reproduced, transmitted, or
stored in any form or by any means, without the prior written consent of the
publisher, except by a reviewer who may quote brief passages in a review or
as provided for in the Copyright Act of 1976.
Computer Science Press. Inc.
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Rockville, Maryland 20850
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Library of Congress Cataloging in Publication Data
Horowitz, Ellis.
Fundamentals of programming languages.
Bibliography: p.
1. Programming languages (Electronic computers)
I. Title.
QA76.7.H67 001.64'24 82-5178
ISBN-13: 978-3-642-96731-3 e-ISBN-13: 978-3-642-96729-0
DOl: 10.1007/978-3-642-96729-0 AACR2
This book is distributed exclusively by Springer-Verlag
Berlin-Heidelberg New York outside of North America, The People's
Republic of China, Taiwan, and Japan.
ISBN-13: 978-3-642-96731-3
Copyright © 1983 by the author. All rights reserved.
So1'tcover reprint of the hardcover 1st edition 1983
2145/3140-543210
Dedicated to
Maryanne, Ruth, Edward,
Cecile, Mom and Dad.
Preface
" .. .1 always worked with programming languages because it seemed
to me that until you could understand those, you really couldn't
understand computers. Understanding them doesn't really mean only
being able to use them. A lot of people can use them without
understanding them." Christopher Strachey
The development of programming languages is one of the finest
intellectual achievements of the new discipline called Computer Science.
And yet, there is no other subject that I know of, that has such
emotionalism and mystique associated with it. Thus my attempt to
write about this highly charged subject is taken with a good deal of
caution. Nevertheless, in my role as Professor I have felt the need for a
modern treatment of this subject.
Traditional books on programming languages are like abbreviated
language manuals, but this book takes a fundamentally different point
of view. I believe that the best possible way to study and understand
today's programming languages is by focusing on a few essential
concepts. These concepts form the outline for this book and include
such topics as variables, expressions, statements, typing, scope,
procedures, data types, exception handling and concurrency. By
understanding what these concepts are and how they are realized in
different programming languages, one arrives at a level of
comprehension far greater than one gets by writing some programs in a
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Preface
few languages. Moreover, knowledge of these concepts provides a
framework for understanding future language designs.
This approach to the study of programming languages is analogous to
the way natural languages are studied by linguists. According to the
linguists Victoria Fromken and Robert Rodman, (in An Introduction to
Language, Holt-Rinehart-Winston), "a linguist attempts to find out the
laws of a language, and the laws which pertain to all languages." In
their book they try to identify the universals of syntax, semantics and
phonology (sounds). But unlike the linguists who see their role as
identifying these universals, computer scientists can hope for more.
The study of the nature of programming languages can lead both to
better understanding of existing languages and also to superior language
designs in the future. The approach taken here hopes to support those
goals.
When Jean Sammet's book Programming Languages: History and
Fundamentals first appeared, with its famous cover of the Tower of
Babel of programming languages, FORTRAN and COBOL were
overwhelmingly used in scientific/commercial computing and in
academia FORTRAN was preeminent. ALGOL60, PUl, BASIC and
others were all being used, but they only accounted for a small
percentage of the programs written in a higher level language. Today
the situation is far more diverse. Pascal and its derivatives are making
major inroads in academic and microprocessor use. PUl usage has
increased substantially. The successful UNIX operating system has
given us a cadre of programmers who know their (A, Band) C. APL
continues to attract a devoted body of followers who use it to solve
every type of computing task. And, many other languages continue to
be used. To further compound this diversity, new languages 100m on
the horizon with the definite possibility of their becoming very
important. I'm thinking in particular of the new U.S. Department of
Defense sponsored language called Ada. The Tower of Babel of '69
which seemed to capture our sense of frustration over the proliferation
of languages has today grown even larger. Thus, it becomes ever more
essential that when we study the subject of programming languages we
concentrate on the fundamental concepts and issues.
Is a comparative study of programming languages possible? The
imperative programming language has now been with us for over 25
years. Many of its concepts are well-understood. Other concepts,
though still controversial, assume a very similar form when the decision
is made to incorporate them into a language. Thus, it is possible to
present a great deal about these languages in an analytical manner.
Other concepts such as exception handling and concurrency are newer
viii Preface
and hence less well-understood. A treatment of these topics can only
hope to present the issues and point out the strengths and weaknesses
of existing language features which support these concepts, but it cannot
provide all the answers.
Though much work has been done on imperative programming
languages, one must not overlook the area of functional programming
languages. As a radically different model of programming they must be
studied. Moreover, the continuing success of LISP indicates that
programming languages based on these ideas have practical as well as
theoretical merit. Nevertheless the bulk of the research on and
development of programming languages has been in the imperative
school and that is necessarily reflected here.
This book follows the guidelines which were stated by the ACM
Curriculum Committee for the design of the course CS 8, "Organization
of Programming Languages." See the Communications of the ACM,
March 1979 for complete details. It is appropriate for undergraduate
computer science majors who have had one year of programming.
Knowledge of Pascal is desirable, but PU1, ALGOL60, ALGOL68 or
something similar are adequate substitutes. The book has also been
used successfully in a first year graduate course whose objective was to
survey the important features of current languages.
I have taught a course based on this book to two different audiences.
The first group consisted of sophomores and juniors with Pascal and
data structures in their background. I had a lab in which the instructors
first taught PUI and then LISP. Programming exercises were included.
In the lectures I worked straight through the book, selecting many of
my examples from PUI and Pascal. I recently replaced PUI by Ada.
The second group consisted of seniors and graduate students in
computer science. There was no laboratory. Instead each student was
given responsibility for a different aspect of a programming language.
For example one student presented an overview of Ada, another
discussed Ada packages and another Ada tasks. There were Pascal,
APL, ALGOL68 and Euclid experts and they all lectured on the salient
features of their respective programming languages. By working closely
with each student I felt I was able to maintain a consistently high level
of presentation.
When discussing a programming language it often becomes essential
to refer to its defining document. This caused me to put together a set
of language reference manuals for my classes. In addition I found it
educational and entertaining to include a variety of articles by well
known researchers. This effort eventually led me to produce an
anthology of source material which I am publishing jointly with this text.
Preface ix
It is called Programming Languages: A Grand Tour. It contains some
classic papers such as the" ALGOL60 report," some controversial papers
such as "Can Programming be Liberated from the von Neumann Style?"
by John Backus, plus overviews of Pascal, Concurrent-Pascal, Ada,
MODULA, C, ALGOL68, CLU, Euclid, FORTRAN77, LISP and APL.
In addition it contains the complete language reference manuals for
Ada, ALGOL60, ALGOL-W, C, and MODULA. I hope the reader and
instructor will find the anthology a useful reference and adjunct to this
text.
A few sentences about Ada seem appropriate. During the time I was
writing this book I watched Ada grow from a requirements document to
a standardized programming language. As I studied the language, I
began to incorporate it into my classes. Now I observe that many of my
examples come from Ada. My main justification is because Ada is one
of the very few languages which has included, in some way, all of the
language features I wish to discuss. Therefore it provides a common
thread, especially throughout the later chapters. This use of Ada caused
me to reprint the entire Ada language reference manual in the
accompanying anthology. Ada will doubtlessly gain a significant share of
the programming language market. Its use here is not an endorsement,
but the recognition of its scope and its growing importance.
Many people have contributed their efforts to the improvement of
this book and I would like to acknowledge their assistance. Of primary
help was the students who attended my classes at USC and at the
Technion in Israel. John Guttag and Barbara Liskov of MIT through
their own course on programming languages were an inspiration.
Several people provided in-depth reviews including Richard Gillmann,
Paul Hilfinger, David Jefferson, and Richard Schwartz. Their insights
supplied a great deal of guidance to me for which I am grateful.
Students Alfons Kemper, Georg Raeder, Simon Wegner and Ronald
Williamson also supplied helpful remarks. Brian Reid and Ray Bates
helped me with the text preparation system, Scribe. And I thank USC's
Information Sciences Institute for access to their facilities.
The study of programming languages is fascinating but not easy.
hope that this book sets people looking and thinking in the right
direction.
Ellis Horowitz
University of Southern California
1982
Acknowledgments
I would like to officially acknowledge and thank the following people
and organizations for granting me permission to reprint various
programs and algorithms: the inner product program of Chapter 1
comes from [Backus 78], reprinted by permission from ACM;
Algorithm 6-7 comes from [Johnston 711, reprinted by permission from
ACM; Algorithm 7-5 reprinted by permission of the author Bob
Schwanke; Algorithm 7-11 comes from [Grune 771, reprinted by
permission from ACM; Structure 8-3 comes from [Hoare 72] reprinted
by permission of the publisher; Structures 8-5 and 8-6 come from
[Chang 78] reprinted by permission of the authors; Algorithm 9-2
comes from [Liskov 79] and is reprinted by permission of the author;
Algorithm 10-6 comes from [Holt 78] and is reprinted by permission of
the author; Algorithm 10-7 comes from [Brinch-Hansen 75] and is
reprinted by permission of the author; Algorithm 10-8 comes from
[Wirth 77b] and is reprinted by permission of the publisher; Algorithm
10-9 comes from [Hoare 78] and is reprinted by permission of ACM;
Algorithms 10-10 - 10-14 come from [Welsh 79] and are reprinted by
permission of the author; Algorithms 10-16 and 10-17 come from
[Welsh 811 and are reprinted by permission of the author; Three
examples of VAL programs come from [Dennis 79] and are reprinted
by permission of the author; Structure 8-7, Table 9-3, Algorithms 6-10,
7-6 and 10-15 and Table 11-6 all come from [Ada 80). Figure 1-4 was
originally conceived and appeared as the front cover of the Jan. 1961
issue of C.ACM and is reprinted by their permission; Figure 7-4 comes
from [Jensen-Wirth]; Algorithm 12-1 comes from [Lisp] reprinted by
permission of the author.
This book was composed and typeset entirely by computer. The text
preparation system is Scribe from Unilogic Inc. and the phototypsetter
was the CAT /4 from Graphics Systems Inc ..
x
CONTENTS
PREFACE...................................................... vi
1. THE EVOLUTION OF PROGRAMMING LANGUAGES.... 1
1.1 Early History. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1. 2 Early Modern History ...................................... 5
1.3 FORTRAN and ALGOL 60 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.4 The Stormy '60s ........................................... 13
1.5 Advances in the '70s. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 22
Concepts Discussed in This Chapter . . . . . . . . . . . . . . . . . . . . . . . . .. 29
Exercises ................................................. 30
2. THE CHALLENGE OF PROGRAMMING LANGUAGE
DESIGN ................................................. 33
2.1 Criteria for Language Design ................................ 35
2.2 Some Possible Solutions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 40
2.3 Imperative vs. Applicative Languages. . . . . . . . . . . . . . . . . . . . . . . .. 45
Concepts Discussed in This Chapter . . . . . . . . . . . . . . . . . . . . . . . . .. 48
Exercises. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 49
3. DEFINING SYNTAX...................................... 51
3.1 The Character Set. ... . . . .. . . .. . .. . . .. . . ... . . . .. . . . . . . . . . .. 51
3.2 BNF ..................................................... 55
3.3 Snytax Graphs ............................................ 61
3.4 Syntax and Program Reliability .............................. 70
Concepts Discussed in This Chapter . . . . . . . . . . . . . . . . . . . . . . . . .. 76
Exercises ................................................. 76
4. VARIABLES, EXPRESSIONS AND STATEMENTS ......... 81
4.1 Variables and the Assignment Statement. . .. . . . . . .... . . . . . . . .. 81
4.2 Binding Time and Storage Allocation. . . . . . . . . . . . . . . . . . . . . . . .. 86
4.3 Constants and Initialization ................................. 90
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