CAD is the use of a wide range of computer-based tools that assist engineers, architects and other design professionals in their design activities. It is the main geometry authoring tool within the Product Lifecycle Management process and involves both software and sometimes special-purpose hardware. Current packages range from 2D vector based drafting systems to 3D parametric surface and solid design modelers. Computers work both quickly and efficiently which allows John E. Sirine and Associates to deliver solutions on Time and on Budget.

Computer-aided drafting, however, commonly refers to the actual technical drawing component of the project, using a computer rather than a traditional drawing board. The input into this aspect of the design process may come from specialised calculation packages, from pre-existing component drawings, from graphical images such as maps, from photos and other media, or simply from hand-drawn sketches done by the designer. The operator's task is to use the CAD software to meld all the relevant components together to produce drawings and specifications which can then be used to estimate quantities of materials, determine the cost of the project and ultimately provide the detailed drawings necessary to build it.