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Reviewer: Erwin Book

Gleaves's book is very well written. This follows the standard the author set in his article, coauthored with Joel McCormack [1]. The book is divided into three major sections, New Concepts, Difference from PASCAL, and Utility Modules. It also contains some summary appendices, among which are the syntax diagrams for MODULA-2. The Module concept, MODULA-2's most significant extension to PASCAL, is discussed first. The rules for exporting and importing are expressed in more detail than in the book by Wirth that defines the MODULA-2 language [2]. The details of scope, visibility, and lifetime are also covered. This book is a useful adjunct to the defining book, even for people who are familiar with MODULA-2. The parts of the book are divided into short cohesive chapters that make for easy reading. The diagrammatic definition of the syntax of MODULA-2 follows the version in Wirth's book. Gleaves follows that book so faithfully that he also does not describe the syntax of a fixed address variable declaration. The book has some minor typographical errors, such as violations of the case rule for identifiers. These do not detract from the overall value of the book. The book is a natural outgrowth of the fact that MODULA-2 is a considerably enhanced version of PASCAL, with the advantages of standardization due to Wirth's name being attached. Because PASCAL has become one of the standard computer languages of recent times, both in the availability of compilers and its use as a basis for more modern languages, a book that teaches MODULA-2 in terms of PASCAL is of great practical value. Whether the book is describing the original MODULA-2 or a particular implementation of the language is not always completely clear. For example, on p. 62 of this book the following statement appears: “Functions may return results of any type.” This conflicts with the statement in the defining book which says, “The result of a function procedure cannot be structured.” Apparently, some language repair work is going on somewhere. This book is a useful adjunct to Wirth's because that book does not explicitly state much of the language semantics explicitly. This book elaborates on those matters. Part 3 of this book, Utility Modules, serves two purposes. The first is to explain certain standard modules that are provided with some MODULA-2 compiler implementations. To paraphrase Wirth, programming in MODULA-2 without the use of library modules is not programming in MODULA-2. The second purpose is as a practical illustration of useful MODULA-2 programming. This purpose is not com- pletely served because the corresponding implementation modules are not shown. I found the book interesting, useful, and easy reading. It serves both as a practical and a conceptual introduction to standard PASCAL programmers on why PASCAL is not a modern programming language.