The Casio FX-991ES Plus is a non-programmable scientific calculator designed for students and professionals in mathematics, science, and engineering. It features a Natural Textbook Display that allows for textbook-style input and output, enhancing readability. With 417 built-in functions, it supports complex calculations including fractions, statistics, regression analysis, and matrix operations. The calculator is powered by both solar energy and a battery, ensuring reliable performance. Its user-friendly interface and comprehensive functionality make it a popular choice for academic and professional use