PURPOSE: To attain simple and clear program description by expressing indentation by a graph such as lines having priority and processing the indentation expression so that functions are divided in accordance with the priority.

CONSTITUTION: Retrieving description in priority lines C0WC8 and detecting the description, an object code forming means sets up '1' in a corresponding bit B0 of a priority register. Retrieving description in an end line C9 and detecting the description, the forming means discriminates the end of the program, and if the program is not ended, discriminates whether the priority line is higher or lower than the current order line. When a line 2 is lower than a line 1, termination processing is not executed and the succeeding line is included in the function of the current line. Since the line 2 is described in the priority line C1, '1' is set up in the succeeding bit B1 concerned in the priority register and the description in the end line C9 is retrieved. If the succeeding higher priority line is described, the termination processing of the program function for the number of bits '1' which is less than the number of bits corresponding to the priority line while referring the priority register to clear bits less than the one corresponding to the priority line of the register.