The last decade has seen an explosion in integrated circuit technology. Improved manufacturing processes have led to ever smaller device sizes. Chips with over a hundred thousand transistors have become common and performance has improved dramatically. Alongside this explosion in manufacturing technology has been a much-less-heralded explosion of design tool capability that has enabled designers to build those large, complex devices. The tools have allowed designers to build chips in less time, reducing the cost and risk. Without the design tools, we would not now be seeing the full benefits of the advanced manufacturing technology. The Scope of This Book This book describes the implementation of several tools that are commonly used to design integrated circuits. The tools are the most common ones used for computer aided design and represent the mainstay of design tools in use in the industry today. This book describes proven techniques. It is not a survey of the newest and most exotic design tools, but rather an introduction to the most common, most heavily-used tools. It does not describe how to use computer aided design tools, but rather how to write them. It is a view behind the screen, describing data structures, algorithms and code organization. This book covers a broad range of design tools for Computer Aided Design (CAD) and Computer Aided Engineering (CAE). The focus of the discussion is on tools for transistor-level physical design and analysis.