Casio FX-991ES PLUS 2nd Edition Scientific Calculator. Here's some information about this calculator: Features: It's a non-programmable scientific calculator with 417 functions, including integration/differential, equation calculation, matrix and vector calculations, complex number calculations, and statistics functionalities. Display: It features a Natural Textbook Display (Natural-V.P.A.M.) that shows mathematical expressions as they appear in textbooks, enhancing understanding. Power Source: It can be powered by both solar energy and a battery. Design: It has a full dot display, plastic keys, and comes with a new slide-on hard case for protection. Target Audience: It's ideal for engineering, polytechnic, and science students.