Programs are described which act as data base manager and editor for libraries of magnetic material descriptions in computer aided design. Curves are modelled by piecewise polynomials with continuous first derivatives. Each material is described by giving its B-H curve and up to three auxiliary (e.g., loss) curves. All material descriptions are identified by user-selected names and titles. Based on fast interactive computer graphics, the editing subsystem permits data entry either numerically or graphically. Various choices of axes, paper distortion, and enlarged plots are permitted. Provision is made for editing, cataloguing, deletion, display, and retrieval of material descriptions. The file management subsystem permits merging or separating the contents of material libraries, as well as exchanging data with external files.