Scientific calculator CASIO FX-991ES PLUS

 
Solar or LR44 batteries, including 417 functions, 4-line screen, 
REPLAY button for reviewing and editing the course of the exercise and calculating formulas,
calculating differentials and integrals,
Calculations and basic vectors (DEC, BIN, HEX),
Converts measurements and scientific constants, fractions, statistics including regression, logical calculations, trigonometry, probability and more,
Options for storing formulas in memory,