Including object-oriented properties in the PLC's programming languages

The PLC programming is designed for a medium user of this equipment. Hence, object-oriented qualities can not be created in the same way established for higher languages like the C++, Java, Eiffel. However, they should fulfil the theoretical principles that govern them. In ALS 4.0 programming language a hierarchy of classes is set in three big trees which include the areas of application of this equipment. Its data and functions are encapsulated with three degrees of visibility (private, protected and public). The dynamic pass of types in execution time is allowed. Persistence is guaranteed outside the creation place and separated from ancestors using the macronets library. However, the whole normalized syntax of the structured languages of the IEC 61131-3 is almost kept. Only the use of object-oriented advantages adapted to the simple level of the standard PLC programming languages will permit the wide diffusion of their features among the PLC users. ALS 4.0 achieves this combination.