PURPOSE: To facilitate maintenance and to generally use a program itself by externally filing one part of an operation sequence fixed in the program.

CONSTITUTION: The operation sequence such as the form of a command to be issued in advance or the contents of analyzing the executed result of the command is registered on an external operation sequence storage file 40 by an input/output device 60 and an external operation sequence storing means 50. Next, before reporting the timing of processing from an external input device 10, the sequence required for the processing is read from the external operation sequence storage file 40 to a main storage device by an input means 20. Corresponding to the processing timing report inputted from the external input device 10 and an operation sequence 30, any relevant operation sequence is selected out of the operation sequences on the main storage device and the processing is executed. Therefore, the operation sequence is made into an external data file. Thus, since it is not necessary to directly deal with the program even when the order of the operation sequence or processing contents are changed, the maintenance can be reduced and the prepared program can be generally used.