PURPOSE: To secure the continuity of work at a terminal.

CONSTITUTION: A picture displayed on a display device 12 at present is preserved in a recorder 8 according to cycle/condition set in a control part or requirement from an input device 14 in a recording control means 7 at the terminal 3 connected to a host computer 1. When the input device 14 requires the display, the preserved picture is displayed instead of the picture displayed at present. Thus, the picture at the specified point of time is optionally referred to regardless of the state of the host computer and a present screen.