CAD (computer-aided design) involves using computers to aid in engineering design. It allows for 2D and 3D modeling/drafting, visualization, analysis such as finite element method simulations, and integration with CAM (computer-aided manufacturing). CAD modeling involves defining objects, their relationships, properties, and orientations. Models are visualized through display/projection techniques and can be analyzed for properties and optimized. CAD requires input devices, output displays, and data storage of curves, surfaces and solids that make up models.