PURPOSE: To decrease data through a communication line network, by fixing fixed data among datas to displaying a control screen to a disc device in a maintenance center in advance.

CONSTITUTION: A service processor 2 receives a request of control screen display to a maintenance center. A screen selection command is produced and transmitted to the maintenance center. A program in a computer main body 7 at the maintenance center picks up a data of the control screen instructed from a command disc 9 and displays the data on a terminal device 8. In completing the display, the program of the maintenance center produces a display completion command and gives it to the device 2. When the processor 2 receives the display completion command, the data other than the fixed data of the control screen, that is, the data different depending on an individually specified state is transmitted to the maintenance center. The program at the maintenance center is displayed to the terminal device 8 as it is, and the display of the control screen is finished.