PURPOSE: To change a definition of one group of data, too, by defining names of various matters of data to be input, as to each key of the data key group, by the display body.

CONSTITUTION: The display body 1 is equipped with the page marks 21, 21,... related to the difinition item pages 1A, 1B, and the timing marks 22, 22,... for performing both the speed reduction command and the stop command. The light emission diodes and the light detecting diodes for the page marks and timing marks 31aW31e, 32a, 32b, and 33aW33e, 34a, 34b are arrayed in the upper direction where the display body 1 passes through. The page is confirmed by moving the display body 1 in response to the command of object page against the definition page of the display body 1, and stopping it at the object page.