PURPOSE: To eliminate the consideration of the level of a routine and positioning of the level at programming, by referencing always the newest common area from a beginning point address of a common memory area stack at each calling level.

CONSTITUTION: A specific common area is set newly to execute the processing at a call level at each calling of each routine in a routine group 5. Common areas 7, 8 of each set level are put together at each routine and formed as the stack of a kind of Last-in-First-Out form. Further, the stack is constituted to make the referencing not only the uppermost stage but the internal stage possible. Beginning point (inlet) addresses 9, 10 of each stack are set to a prescribed location in a common area 6 of a program A. Each routine references an optional common area of other routines via the beginning point addresses for using the data.