PLC- Determine the Sequence of Operation

We have to identify the equipment or the system to be controlled. The ultimate purpose of the
programmable controller will be to control an external system. The system to be controlled may be machine,equipment, or process to be controlled.The movement of the controlled system is monitored
in real time by the input devices. It gives a specified condition and sends a signal to the programmable
controller. The programmable controller outputs a signal to the external output devices which actually
controls the movement of the controlled system as specified and thus achieves the extended control action. In simple, one needs to determine the sequence of operation in steps form for onward development of flow chart by completely understanding the system detailed operation.