PURPOSE: To make it possible to push the switch exactly and swiftly, by covering the keyboard with a rubberlike molded sheet which can be detached and attached only when required, and has the symbols assigned to the push-button switches and printed on it.

CONSTITUTION: In case of regular registration of goods, when the key top 3 is pushed in a state that there is no molded sheet 5, the push-button switch 2 is turned on and the operation is performed. In case when it is required to set in advance the printing contents of a printer, etc., that is, in case of installing an apparatus, etc., No. assigned to the push-botton switch 2 is varied by changing the internal switch of the apparatus. In this case, said operation is executed by covering the key top 3 with the molded sheet 5 made of rubberlike soft material, which can be detached and attached, and has the symbols assigned to the push-button switches and printed on it, and pushing the key top 3 related to the display contents of the molded sheet 5.