PURPOSE: To shorten the window operation time by operating a similar processing to entire related windows by performing an operation to one window.

CONSTITUTION: This device is equipped with a window management list 20 constituted of a window ID21 and node number 22, node information list 30 constituted of a node number 31 and window information 32, node relation list 40, and data connection relation managing means which manages the connection relation of data. The window information 32 is equipped with a window ID32-1, classification 32-2, size 32-3, preparing time 32-4, protection information 32-5, number of link 32-6, and relation list pointer 32-7. In the window relation list, higher-rank layer, window itself, same-rank layer, and lower-rank layer are expressed by a node division 41 for classifying the window to be referred to and the related windows, and specifying the hierarchical structure of the classified windows by upper-and-lower relation.