1. A calculation device configured to allow a user to quickly and efficiently change the way an expression is displayed, the calculation device comprising: entry keys configured to allow a user to enter various mathematical expressions; a display configured to display mathematical expressions; and a processor configured to receive entry key inputs in an entry mode and display a mathematical expression representing the entry key inputs on the display, the processor further configured to determine and display a result to the entered expression in a result mode, wherein when the processor is in the result mode, entry key inputs received by the processor are interpreted differently then in the entry mode.