6. A calculation device comprising: entry keys configured to allow a user to enter at least a formatted mathematical expression; a display configured to: display the formatted mathematical expression, and display an editing cursor that the user can move to various locations within the display, the various locations including a plurality of locations within the formatted mathematical expression; a hardware processor, wherein the hardware processor operates the display in at least a bipositional input mode, wherein in bipositional input mode when an entry key actuated by the user is a character key, a character corresponding to the character key may be inserted in any of the plurality of locations of the formatted mathematical expression.
6. A calculation device comprising: entry keys configured to allow a user to enter at least a formatted mathematical expression; a display configured to: display the formatted mathematical expression, and display an editing cursor that the user can move to various locations within the display, the various locations including a plurality of locations within the formatted mathematical expression; a hardware processor, wherein the hardware processor operates the display in at least a bipositional input mode, wherein in bipositional input mode when an entry key actuated by the user is a character key, a character corresponding to the character key may be inserted in any of the plurality of locations of the formatted mathematical expression. 11. The calculation device of claim 6 , wherein when the processor operates the display in bipositional input mode and a character most recently entered by the user is a last character of the formatted mathematical expression, then if a next key actuated by the user is a digit key then a digit thus actuated is inserted as a new last character of the formatted expression, but if the next key actuated by the user is one of a plus key and a minus key then a character thus actuated is inserted outside of and immediately following the formatted mathematical expression.