AutoCAD is the most widely used computer-aided design package in the world. Underneath AutoCAD is a powerful computing language called AutoLISP. This language is designed to automate many functions of AutoCAD. This book is a hands-on introduction to AutoLISP and its applications. AutoLISP is a unique and powerful language that allows you to write, debug, and modify programs extremely quickly, once you understand how the language itself works. Part I contains an easy-to-learn pictorial representation for data and code, a tool used to easily solve problems otherwise approached through trial and error method. Essential AutoLISP is the only book in its field that uses the pictorial representation. Part II is devoted to learning how AutoLISP processes the code entered. Part V not only explains the causes of most common error messages and how to solve them, but examines many other errors that don't necessarily give messages.