PURPOSE: To speedily call the data processing function by displaying a list of items on a display screen, calling a corresponding data processing function according to a selection instruction to an item, and performing a calling process.

CONSTITUTION: When there is a processing request from a user, a user processing program 24 calls a screen process execution program 23 and instructs the execution of an interactive process with the user. When the control is thus passed, the program 23 displays the list of items on the display screen and detects the click operation of a mouse on the display to performs the specific process of the item selected by the user, and a screen definition body 22 whose use is declared successively is referred to and the attention name of this item is reported to the attention area of the program 24. The program 24 calls the program 20 corresponding to the attention name and performs the data process. This operation is repeated.