Introduction

This textbook is for beginning Smalltalk programmers using ParcPlace Digitalk's VisualWorks Smalltalk and ObjectWorks Smalltalk. It contains many examples programs with detailed explanations. 'Engi' is a Japanese Buddhist word which means "everything in the world is related to each other." So, "Engi" is used as a prefix for every class in this textbook to symbolize that this textbook may strengthen your relationship with Smalltalk.

The intended reader is the beginning programmer who understands the syntax and tools of Smalltalk but does not understand how to use the vast array of classes which VisualWorks offers. Many Smalltalk programmers have complained that there is no good easy-to-understand textbook for VisualWorks and ObjectWorks (especially in Japanese.) And students in universities have also difficulty acquire Smalltalk programming skills because of the lack of a good introductory textbook. I sincerely hope this textbook is useful for these people.

This book does not go into the details of VisualWorks and ObjectWorks. In fact, I recommend that Smalltalk beginners do not waste time investigating the innards of VisualWorks and ObjectWorks. Your time is much better spent writing new programs. The Smalltalk labyrinth is deep and you will disappear for 1 or 2 years before returning to this world. Instead, I hope you will learn many things about Smalltalk by extending the examples. I would like you to do one thing after you work through each example and that is to try to use the 'senders' and 'implementors' commands. You will find these commands in the launcher and yellow-button-menu of the message pane (right end window) of the browser. You can learn much about the usage of a message and the objects that can receive that message by using 'senders' and 'implementors'. One sign of a good Smalltalk programmer is his or her skill in using 'senders' and 'implementors'.

Object-Oriented programming is a cutting tool. Objects and messages are the knife with which you cut everything; it is how you classify and understand things. The power of an object is it's distinction from all other things. Sometimes you must cut a thing that in fact is impossible to cut. In this particular sense the concept of Object and Message is a sharp sword. I would be pleased if this textbook helps you master the quintessence of Object-Oriented Programming.