PURPOSE: To ensure the program development in an extremely short period without using any device for the program development but by interpreting directly the program described in the high-class language via the microprocessor for execution.

CONSTITUTION: The basic language is coded into the binary number and then stored in program memory 1. At the same time, the contents are reset for program counter 3 and microprogram counter 4 by resetting the microprocessor, and the initial value is set to stack point 9. Then only the interpretation is advanced for program meory 1 from the zero address toward the higher-rank addresses in sequence and based on the control program stored in ROM2, and at the same time the sentence number address table and the variable tabe are formed into RAM7. The reservation work table is provided at ROM2, and the words having no coincidence are registered in the variable table. After this, the read-in of the source program is started from the address of the sentence number address table to execute the interpretation of the sentence.