A new computer-related system that can be used by design engineers to perform both simple and complex descriptive geometry calcuations is described. The system, which requires no special programming knowledge on the part of the engineer, includes a free-cursor digitizer and a “menu” of calculations which are used in conjunction with conventional drawings to define various computations for the computer. The system eliminates the normal problems of graphic-to-digital conversion associated with existing methods of computer-aided design, thus freeing the engineer from hours of tedious and routine work.