Abstract: The present invention is intended to enable an electronic calculator device for calculating functions to display a mathematical expression by automatically substituting a variable-value into a variable therein in advance. An electronic device comprises an input device for inputting a mathematical expression containing a variable, a store device for storing a value of the variable and a display device for displaying a mathematical expression on a display screen. The electronic device is further provided with a converting device for reading a value for a variable contained in a mathematical expression from the store device and substituting the read-out value into the variable in the mathematical expression to be displayed on the display screen.