Computer-aided design (CAD) is the use of computers to aid in the creation, modification, analysis, or optimization of a 2D or 3D design – drawings may be created in 2D or 3D and then get printed out full size or to scale. The drawing of engineering components, infrastructure designs and systems plays a major role in most engineering fields and is therefore an essential skill to learn and master. The free version of Sketchup is used for demo purpose in this book.