9. An apparatus for performing calculations in a character input mode of a electronic device, comprising: a display unit displaying input characters in a character input window in the character input mode; and a control unit determining whether a preset calculation enabling condition is satisfied, checking whether an arithmetic expression is present in the displayed input characters, evaluating the arithmetic expression when the preset calculation enabling condition is satisfied, and controlling the display unit to display a result of the evaluation.
12. The apparatus of claim 9 , wherein the control unit controls the display unit to present the identified arithmetic expression in a manner distinct from the remaining portion of the displayed input characters.