Ladder, FBD, ST, SFC: 4 PLC Languages Engineers Still Use in 2026
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What are the four main PLC programming languages and when should I use each?
The four normative IEC 61131-3 languages , LD for discrete and safety, FBD for process loops, ST for math and data, SFC for batch and state machines , cover every controller duty on current platforms.
Detail
, still cover almost every controller KOEED ships. They are the four normative languages from
that every modern vendor IDE (Studio 5000 v36+, TIA Portal V20, GX Works3, Sysmac Studio) implements, plus a handful of vendor-specific dialects that are still useful to recognize on legacy and brownfield lines. This 2026 update walks through what each language is for, what changed since the 2024 edition of this article, and which one to reach for on a
, LD, FBD, ST, SFC , cover discrete I/O, process loops, algorithms, and state machines on every modern controller.
still wins for wiring, motor starters, and safety circuits that maintenance electricians must read with a printout at 02:00.
is now the default for math, recipes, IIoT payloads, and any code that needs OOP extensions or refactoring tools.
in Studio 5000, Siemens S7-SCL, Mitsubishi GX Works3 ST , map cleanly onto the IEC 61131-3 base.
In 2026 the four IEC 61131-3 languages still cover the same control problems, but the recommended mix is ST for code, LD for wiring, FBD for loops, and SFC for sequences.
Studio 5000 v36+, TIA Portal V20, GX Works3, and Sysmac Studio now expose Structured Text with full OOP, namespaces, and refactoring tools on par with C# or Java. SFC gained clearer branch and step-action semantics in the 4th edition of IEC 61131-3 (IS 2025), which removes a long-standing source of confusion.
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