This book is the definitive description of the Smalltalk:U80 system. Smalltalk was originally developed by the Xerox Learning Research Group in the early 1970s. At that time, the system was used as a vehicle for teaching programming to children. In this latest incarnation, however, it has evolved into a system for prototyping and building systems.:P I say Smalltalk:U80 :Isystem rather than :Ilanguage, because what the book describes is considerably more than a programing language. The first part of the book:Vroughly an eighth:Vdescribes the Smalltalk:U80 langage :Iper se. One might think of this as an outgrowth of SIMULA with type variables but without variable declarations, and with terminology and syntax drastically changed. The second part of the book-Va bit less than half:Vdescribes the presupplied classes (types) and methods (functions). These are extensive, comprising numbers, characters, symbols, arrays, bags, sets, dictionaries, streams, processes, various geometric objects, and bitmaps, among others. The second part also gives a brief description of the user interface, which is a version of the increasingly familiar overlapping windows on a bitmapped display screen with keyboard and mouse input. (Indeed, the first Smalltalk systems were the earliest examples of such now commonplace features as menus and scroll bars.) Harking back to Smalltalk’s roots in SIMULA, the third part of the book presents an extended example of building and using a framework for discrete event simulation.:P Finally, the fourth part of the book describes the implementation of the Smalltalk:U80 virtual machine. The Smalltalk:U80 system consists of a relatively small virtual machine and a rather large :Ivirtual image which is essentially a snapshot of a running Smalltalk:U80 system. Most of the system is written in Smalltalk:U80 itself and resides in the virtual image in the form of an intermediate representation executable by the virtual machine. Implementing Smalltalk:U80 on a new machine consists of reimplementing the virtual machine and obtaining a copy of the virtual image from Xerox Corporation.:POn the whole, the authors have written a fairly good guide and introduction to Smalltalk:U80. As a reference manual, however, the book leaves something to be desired; there are numerous omissions of detail, and descriptions of individual functions tend to be buried in prose. This is expecially true in the second part (on the standard classes.:P To a certain extent, the omissions in this part are understandable given the philosophy of using the Smalltalk:U80 system. Programmers ar not expected to write entire programs and then run them through, burt rather to build them interactively. Since most of the standard classes and methods are implemented in Smalltalk, their text and descriptions are available online through :Ibrowsing facilities that are part of the user interface.:P The first part (on the language) is essentially complete. The fourth part (on implementation) is a complete description of an unoptimized implementation. For completeness, implementors will also need the collection of implementation studies and advice edited by Krasner [1]. The reader will also find little detail on the user interface and debugging facilities. These topics are covered in another book by Goldberg [2].:P Limitations notwithstanding, the book under review is indispensable for anyone interested in using or implementing Smalltalk:U80.:L

REFERENCES

[1] KRASNER, G. (Ed.) :ISmalltalk:U80: bits of history, words of advice, Addison:UWesley, Reading, MA, 1983. See :1ACR this issue, Rev.

[2] GOLDBERG, A. :ISmalltalk:U80: the interative programing environment, Addison:UWesley, Reading, MA, 1983.