the calculator's keyboard can be separated into the lower, middle, and top parts. the lower part of the keyboard consists of numeric and operational keys, where the exe button is used to execute calculations and select commands. the middle part contains more sophisticated mathematical function keys, shift and alpha keys, and directional pads. the shift and alpha keys are used to access functions and alphabets appearing on top of buttons. the top part consists of buttons f1 to f6, used to select function menu tips.