PURPOSE: To shorten an error analytic and command input time and to improve the efficiency of error processing by outputting error information at a time at the stage of the completion of a check on all parameters when there are plural errors in commands including plural parameters.
CONSTITUTION: A command is inputted to the command processing part 10 in a processor 1 and a parameter error detecting means 11 checks plural parameters in order. The parameter error detecting means 11 even if an error is detected in one of the parameters does not quit the processing of the input command and starts checking a next parameter to store error information in an error information storage means 12 every time an error is detected. All parameters are checked and if parameters errors are stored, the error information stored in the error information storage means 12 is all read out in order and sent out to an input/output terminal 2. Consequently, the error analytic and command input time can be shortened.