Electronic device and method of displaying mathematical expressions including variables

A method of displaying a mathematical expression including a variable, used with an electronic device having an input unit for inputting a mathematical expression including a variable, a memory device for storing a value of the variable, the memory device including a first buffer for storing the mathematical expression and a second buffer for expanding the stored mathematical expression into a character string to be displayed, and a display unit for displaying the mathematical expression on a display screen, the method comprising the steps of:

• reading the value of the variable from the memory device;
• substituting the variable in the mathematical expression to be displayed on the display screen with the value of the variable read from the memory device;
• storing the mathematical expression in the memory device;
• and
• selecting between a first mode of displaying the mathematical expression stored in the memory device on the display screen by the display unit after substituting the read-out value for the variable and a second mode of displaying the mathematical expression on the display screen by the display unit with the variable displayed in terms of a variable-name, using a change-over key included in the electronic device, thereby allowing a user to change the mode of displaying the mathematical expression on the display screen by successively actuating the change-over key.