Introduction to Industrial Automation

Figure 7.7  Structure of an automation program according to the IEC61131-3 standard.

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Basic Programming Principles of PLCs 

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reuse of the same FBs. The reuse of ready-made FUNCTIONS and FBs, developed by users, sig-

nificantly reduces the programming and debugging time required and therefore the correspond-

ing development costs.

Regardless of the IEC 61131-3 standard and its influence on the PLC manufacturers, the soft-

ware development for PLCs is following, with only a little delay, the software being developed for 

PCs. Therefore, those who are already familiar with programming languages such as C and C++ 

will not have a particular problem with the concept, definitions, and implementation of structural 

programming.