PURPOSE: To improve the productivity a flexibility of software by connecting cables to input and output terminals of a basic unit optionally corresponding to a requested sequence, in a stored-program controller.

CONSTITUTION: In arranged basic units 100WKOO, processors 20 stored with the same or different programs, and two-way data buses 31W3N and 41W4N of I/O ports 21W2N are connected mutually, and the said input and output data buses 31W3N and 41W4N are connected to input and output terminals. Then, input and output terminals of those basic units 100WKOO are connected optionally by detachable cables corresponding to a requested sequence that a controller has, and plural part programs are executed by different processors 20 in series or parallel.