To allow a PC(programmable controller), which does not have a process stepping function(SFC), to perform the process stepping action(SFC) without adding any special instruction.

Once the PC runs, Y0 automatically turns on first, X0 as a transition condition turns on with a push-button switch PB0 on and Y1 as a transition destination is set(SET), namely, Y0 as a transition source is reset(RST). With a push-button switch PB1 on, X1 as a transition condition turns on and Y2 as a transition destination is set(SET), namely, Y1 as a transition source is reset(RST). With a push-button switch PB2 on, X2 as a transition condition turns on and Y0 as a transition destination is set, namely, Y2 as a transition source is reset(RST). At this point of time, the PC is put back in the initial state of RUN. This action is repeated thereafter.