PURPOSE: To reduce excess area and to effectively utilize a memory by composing a second storage means of more than one block making up a constant number of merchandise into one block.

CONSTITUTION: An unpaid information file 32 is divided into common area 31 of an unpaid information file storing the sum of money, etc., and a menu file 33 storing registered menu (merchandise). This menu file 33 is composed of a constant number of menu blocks 34, and an arbitrary number of menu blocks 34 can be used in one unpaid information file 32, and either of unpaid information files 32 can use the menu block 34 when there is an unused menu block 34. So, when the number of menu increases to run short of the one block, a new block can be added and it is not necessary to fix the number of menu per one unpaid information file 32. Thus, the excess memory is reduced and the memory can be effectively used.