A procedure (user program) in which a PLC 2 controls operation of input-output apparatuses (4) is generated on a ladder window by using a ladder editor (32a). A screen (user screen) on which a programmable display apparatus (1) displays states of the input-output apparatuses (4) is generated on a screen generating window by a screen generating editor (32b). For example, when a symbol on a ladder diagram on the ladder window next to the screen generating window is dragged and dropped onto the screen generating window, attribute data including a name and address of the input-output apparatus that relates to the symbol is copied from a ladder file (33a) for registering the user program to a screen file (33b) for registering the user screen, and a mark corresponding to' the attribute data is displayed on the screen generating window. This eliminates a need of a common database for registering the attribute data.