Computer-aided design (CAD) services assist in the computerized design, three-dimensional (3D) modeling, and printing and drafting of engineering components and assemblies. Computer-aided (CAD) services include specialized programs that help operators draw schematics for printed circuit boards (PCB), electronic or mechanical components, and systems for computer aided manufacturing (CAM). Some companies specialize in analog design or backplane design. Others specialize in 3D modeling.