Programmable Logic Controllers A Practical Approach TO IEC 61131...

As long as there have been competing producers of PLCs on the market, there have been different programming languages from one PLC brand to another. Even though the same languages, beginning with Instruction Lists (IL) and Ladder diagram (LD), have been used by most of the producers, all of them added their own “dialects” to the languages. When physical programming terminals replaced software‐based programming tools, the differences between languages of the various producers escalated. Several programming languages also saw the light of day. This development was the natural result of the attempt by the producers to make themselves stand out among increasing competition by developing the most user friendlylanguages and tools.