In the present invention, a map information table is displayed as a list on a display screen. The map information table associates a reference name field representing each of the plurality of device ports with a set value field for each device port. It is determined whether a set value has been written on the set value field for each of the device ports regarding a first program in a first programming language. Writing of a set value on the set value field is prohibited regarding a second program in a second programming language, which is different from the first programming language, for a device port for which it is determined that a set value has been written on the set value field regarding a first program in the first programming language.