The application of computer technology to the design of a product, or the design itself. Computer-aided design is used especially in architecture and electronic, electrical, mechanical, and aeronautical engineering. A computer-aided design uses as inputs both the appropriate technical knowledge of individuals who enter design criteria, edit results, and otherwise test and modify the design, and also accumulated information from libraries of standards for components, element sizes, regulations, etc., such as standard ICs for a digital design system or standard pipe lengths and fittings for a hydraulic or piping system. Processing of the data from the inputs takes place in at least two phases:

1. (a) certain interactive programs are invoked by the technical designer during the design process, these results being generally displayed on a VDU;

2. (b) programs are applied that may take considerable periods of running time to analyse tolerances, clearances, electrical characteristics, etc., the results of these runs being displayed back to the technical designer.

Output from a computer-aided design system consists of printouts of specifications and other information, and machine-readable files that are passed to computer-aided manufacturing (CAM) systems and computer-aided testing (CAT) systems. Examples of output to a CAM system are computer-produced artwork for printed circuit boards, or computer-produced tapes for automatic component insertion and board drilling. The combined process of computer-aided design and manufacture is known as CADCAM. The whole procedure—design, manufacture, and testing—is often referred to as CADMAT. There is an ISO standard (STEP) for the exchange of product model data, including CAD data.