PURPOSE: To make it easy to understand the operability without the extension of the boundary line of a denominator and a numerator and the movement of a cursor to the extension part for the movement of the cursor on the mixed fraction displayed as per the formula.

CONSTITUTION: When a cursor 31 of a horizontal under line is moved from the right edge of an integer part A (numerator part B) to the left edge of a numerator part B (denominator part C), the mode is changed to a half-tone dot meshing cursor 31a by a first operation of a cursor right moving key 33, a cursor displaying position is moved by a second operation and returned to the cursor 31 of the horizontal under line. When the cursor 31 of the horizontal under line is moved from the left edge of the denominator part C (numerator part B) to the right edge of the numerator part B (integer part A), the cursor displaying position is moved by the first operation of a cursor left moving key 32, the mode is changed to the networking cursor 31a and returned to the cursor 31 of the horizontal under line by the second operation.