The Casio FX-991ES Plus is Casios most advanced scientific calculator with 417 mathematical functions. Recommended for Advanced GCSE, A/AS Levels and Highers. Dual powered (solar with battery back-up). This advanced model allows Matrix, Equation, Integration and Differential calculations as well as Random Integers, Scientific Constants and Metric Conversions. The large natural texbook display (Natural V. P. A. M. ) shows mathematical expressions as they appear in your textbooks. Suitable for GCSE, A Level and above. LCD display. 9 data memory. Non-stick keys. 10+2+15 -digit display. Auto shut-off. 417 functions. Verify function. Algebraic logic. Regression analysis. Statistical functions. Hyperbolic. 24 levels of parenthesis. Metric conversions. Dual power source - solar and battery. General information: Batteries required 1 x button cell (included) . Manufacturers 3 year guarantee.