This is the famous 'Blue Book' which every serious Smalltalker should have on their shelves to show off as a historical document of the highest order; but not only for that reason. It provides a superb vision and clear description of the Smalltalk language and environment. It's dated in places, but that only adds to its appeal. Serious programmers can only gain from seeing how things were done at the dawn of Smalltalk. Most importantly, and uniquely, it defines a complete reference implementation for the original Smalltalk-80 Virtual Machine that ran the original Smalltalk-80 Image. The reference code is all in Smalltalk and was written for clarity, not performance --modern Smalltalk VMs have optimisations making for high performance but it is difficult for beginners to see beyond these features to understand the basics. This book is now out of print and should not be confused with Smalltalk:The Language by the same authors (the Purple Book). The Blue Book's contents: Part One - overview of programming language( concepts and syntax) Part Two - specification of the system's functionality Part Three - design and implementation of a moderate-size application Part Four - specification of the Smalltalk-80 virtual machine The Purple Book is the Blue Book minus part four. In some senses the Blue Book is bang up to date, for instance the GNU herd specify it as their main reference, to quote: 'GNU Smalltalk is an implementation that closely follows the Smalltalk-80 language (tm ParcPlace Systems) as described in the book `Smalltalk-80: the Language and its Implementation'..."the Blue Book"'.