PURPOSE: To monitor and control processes easily, quickly and safely by preliminarily making a multiwindow picture for registration and displaying the register picture again according to need.

CONSTITUTION: After a picture is made through multiwindow picture generation and processing 2, a layout table 9, 10 is generated through layout table preparation and processing 6; in this layout table 9, 10, the coordinate of a display window and the picture numbers to be shown in each display window is stored. Then, the layout table 9 is preserved through multiwindow picture registration and processing 7, and is also registered in a function key 11 on an input device 4. After that, with the function key 11 pressed down, the re-display processing 8 of the multiwindow picture is carried out, displaying the multiwindow picture. Consequently, the secure monitoring of processes is made possible by displaying the multiwindow picture easily and quickly.