The Casio fx-991CW is a non-programmable advanced scientific calculator ideal for students in mathematics, science and engineering.
Key features include:

• Natural Textbook Display: shows fractions, powers, roots etc. just as they appear in textbooks.

• High resolution dot-matrix LCD with a 4-gradation (four tones) display for clearer input cursor tracking.

• Dual power: solar cell + battery backup, with automatic power-off to save energy.

• Over 540 built-in functions: supports advanced operations such as matrix & vector calculations, complex numbers, numerical integration & differentiation, equations (simultaneous & polynomial), statistical calculations, spreadsheet-style lists, and more.

• Smart connectivity feature: can generate a QR code of an equation which you can scan on a smartphone/tablet to graph or visualize it via the online service ClassPad.net.

• Compact and lightweight: dimensions ~162 × 77 × 10.7 mm, weight ~95 g.

• Comes with a hard sliding cover to protect the unit.

• Exam-friendly: As it’s non-programmable and non-graphing (aside from QR code output), it is permitted in many school and university exams.

In summary:
If you’re looking for a reliable calculator for advanced high-school or tertiary studies (GCSE/A-Level, engineering), the Casio fx-991CW offers excellent functionality, strong features and modern display convenience in a compact form.