Two-way power (Solar + Battery). Solar powered when light is sufficient, battery powered when light is insufficient. Plastic keys. Designed and engineered for easy operation. S-V.P.A.M. (Super Visually Perfect Algebraic Method). All the features of the existing V.P.A.M. series plus a new 2-line display and a useful Replay function. All this helps to make mathematics easier to use and easier to understand than ever before. STAT-data editor. Back-step viewing and editing of input data.