The language interface defines all the data which can be read or modified by the application program. The data is implicit and periodic (%Q, %QW, %I, %IW) when it is updated automatically by the PLC task. It is explicit and aperiodic (%MW) when it is updated by the program after execution of the READ_STS or READ / WRITE_PARAM functions.

It is possible to associate with each word or bit a symbol which can be used by the application program. A table of symbols has been predefined. They can be assigned to the module data. For more information refer to EcoStruxure™ Control Expert, Program Languages and Structure, Reference Manual.