CAD stands for computer-aided design. In CAD, software programs and a variety of input devices are used to make detailed design drawings for architecture, electronics, engineering, and manufacturing.

CAD programs vary in complexity. The simplest CAD programs provide an electronic drafting tool, a means for drawing objects with great detail. The drawings thus made are so precise and accurate that they can be used to construct the actual object. More complex CAD programs can be used to draw three-dimensional models of an object. Using the more complex CAD programs, designers can adjust and test various aspects of the design on the computer screen even before the object is constructed.

CAD had its origins in computer graphics programs developed in the 1950s at the Massachusetts Institute of Technology for the United States Air Force. Prior to that time, drafting was done with pencil and paper...