Computer-aided design (CAD) is the use of computer technology for the design of objects, real or virtual. CAD often involves in the manual drafting of technical and engineering drawings, the output of CAD often expresses symbolic information such as materials, tolerances, processes, and dimensions, according to application-specific conventions. CAD is used to design curves and figures in two-dimensional (2D) space; or curves, surfaces, or solids in three-dimensional (3D) objects.