a) Conductor: Polymorphism
The conductor data-type has a direct physical counterpart. A
physical copper or aluminum wire, for example, can carry data of
different types: digital, analog, even data frames multiplexed in the
time or frequency domain. In the same way, the conductor object, as
defined in Figure 1, can carry any type of the elemental data defined
in the IEC 61131-3 standard. There is a drawback in this definition:
the size of a conductor structure is the sum of the size of each
elemental data type that it can hold. The solution to this problem
could be the addition of a new data structure to the standard, included
in modern OOPLC languages such as C++: the “union” type, whose
size is only the largest size of any of its elements.