Which PLC Programming Languages Are Used Most Frequently?

PLC Programming Languages usages

The International Electrotechnical Commission, also known as IEC, Section 61131-3 Standard is written in all five languages that are included in its vocabulary. This IEC Standard establishes certain basic principles that standardize PLCs as well as the languages used by them. Let’s go a little more into each of these popular PLC Programming Languages, shall we?

Top 5 PLC Programming Languages

1)    Ladder Diagram (LD)

2)    Sequential Function Charts (SFC)

3)    Function Block Diagram (FBD)

4)    Structured Text (ST)

5)    Instruction List (IL)

Let us demonstrate each of these things a little bit to you. We will begin with Ladder Diagram, a sort of PLC Programming Language represented graphically.

1) Ladder Diagram (LD)

The initial paradigm for the Ladder Diagram was derived from relay logic, which controlled operations using physical devices like switches and mechanical relays. Ladder Diagram’s internal logic replaces everything but physical devices, which require an electrical signal to be activated.

On relay-logic schematics, the electrical connection is represented by two vertical rails. The Ladder Diagram is constructed in the shape of horizontal rungs with vertical rails. You can program all of the essential input requirements to influence the output requirements, regardless of whether or not those requirements are logical or physical.

2) Sequential Function Charts (SFC)

Suppose you are already familiar with flowcharts. In that situation, you will find that this PLC Programming language feels quite comfortable. When working with Sequential Function Charts, you will accomplish your targets using steps and transitions.

ü Your application relies heavily on the steps you take to complete certain tasks. Essentially, these steps are where the activities will take place after you have programmed them to occur. This choice may be influenced by the timing of events, a particular operation stage, or the equipment’s actual physical condition.

ü Meanwhile, instructions you follow to go from one step to the next by establishing either true or false conditions are referred to as transitions.

Sequential Function Charts, in contrast to more conventional flowcharts, allow for more than one solution. You may begin more than one step at a time by using branches in your process.

3) Function Block Diagram (FBD)

The Function Block Diagram is a form of graphical language in its own right. Fundamentally, a function is described using the Function Block Diagram, wherein inputs and outputs are represented as blocks linked to one another via connection lines.

Function Blocks were designed and created to make it easier to configure various common functions, including timers, counters, and PID Loops. You will then program connections between the blocks using the sheets. The PLC will continually scan the sheets in the correct sequence or based on the links you have programmed between the blocks.

4) Structured Text (ST)

Structured Text is the fourth PLC Programming Language that has been developed. This language relies heavily on written communication. The high-level programming language, Structured Text, is comparable to Basic, Pascal, and “C.” It is a strong tool that can perform strenuous activities employing algorithms and mathematical calculations along with repeated chores.

In the code, statements are denoted by semicolons and are used to make changes to inputs, outputs, or variables. These statements are separated from one another by semicolons. It requires you to write each line of code and use operations like WHILE, FOR, IF, ELSE, ELSEIF, and CASE.

This PLC Programming Language will seem simpler to you than some other kinds of PLC languages, particularly if you have previous familiarity with the basic programming languages.

5) Instruction List (IL)

Instruction List, the last and fifth PLC Programming Language, is presented here. Like its predecessor, Instruction List is a textual-based language.

The language of the Instruction List is quite similar to Assembly Language. It would help to use mnemonic codes to operate inside this PLC Programming Language. Some examples of these codes are LD (Load), AND, OR, etc. The Instruction List comprises instructions, each presented on a separate line and followed by a space at the end of the line for any comments.


The Ladder Diagram is by far the most widely used PLC programming language. The primary explanation for this is that the Ladder Diagram just happened to follow naturally in the footsteps of the technological evolution from physical relay logic to a virtual and logical one. The skilled workers and engineers could follow along, troubleshoot, and complete the transformation.

In conclusion, each of the PLC Programming Languages we have looked at has its specific use. Your prior knowledge and experiences and the nature of the application you want to use will be the most important factors to consider while selecting a PLC Programming Language.

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