PURPOSE: To eliminate the need for changing a screen display program when a screen is added and the attribute of an input/output item is changed by giving information on an input/output screen in a file and setting a processing for actually executing plotting to be an independent process processing.

CONSTITUTION: When a request for inputting data to the input screen in a job processing 4 is given to a screen control processing 10, the screen control processing 10 reads the corresponding screen information file 6, table-displays it in a display 3 and develops an item information file 7 in a memory. When there is input to the input screen from a keyboard 11 and a pen touch keyboard 12, the job processing 4 sets input information in an item information table by a screen control interface 8 and gives a notice for which item data are inputted to the screen control processing 10. The screen control processing 10 analyzes the notice, refers to the content of the item for which data are inputted in the item table 9 and changes/displays the item in the input screen displayed in the display 3. A screen editing processing 5 generates the added screen.