variational finite elements and boundary-integral methods for electromagnetic field analysis require large amounts of data to describe the device under design, to build a mesh model, and to display useful results. In order to manage these data, interactive definition, subdivision, and results-display programs have been built. With the first program the user can build a geometrical description of a device which is used in the second program to create a mesh model by isoparametric mapping. Results from field analysis are then displayed as equipotential lines on a surface chosen by the user. In order to sucessfully management, routines linkage, and command language.