Plc designing apparatus

A PLC designing apparatus formed on a computer including a pointing device and a display device by the computer executing an editor program and configured to design a programmable logic controller having a multi CPU configuration including a plurality of CPU units, the PLC designing apparatus comprising:

• an editor-screen display unit configured to cause the display device to display a list of one or more units applicable to the programmable logic controller;
• a unit-configuration display unit configured to cause the display device to display a model indicating an arrangement state of the one or more units of the programmable logic controller;
• a unit-selection/arrangement-input detecting unit configured to detect unit selection operation for selecting a unit in the unit list using the pointing device and unit arrangement operation for designating a mounting position of the unit, which is selected by the unit selection operation, by operating the pointing device in a state in which the unit selection operation is maintained;
• and
• a management-CPU-determination processing unit configured to determine a CPU that manages the unit selected by the unit selection operation as a CPU included in a CPU unit in the model with which a pointer comes into contact during the unit arrangement operation.