Abstract: A calculator which can display not only numerical digits but also arithmetic operational signs and functional symbols. A display portion of the calculator has a numerical value display portion on its lower side and an expression display portion on its upper side, wherein a cursor appears only in the expression display portion. Any digit inputted from numerical keys is first displayed at the numerical value display portion, and such a digit is inputted into the expression display portion when a key for giving instructions to perform an operation is depressed. A CPU clears all of input numerical digits displayed at the numerical value display portion and shifts a cursor back to an end of a mathematical expression displayed at the expression display portion when a cursor-left-shift is operated. When a cursor-right-shift key is operated, the CPU deletes a digit located at the lowest position of the numerical value display portion.