File Fill

Fills destination array with copies of single source value. This term is essential for understanding ladder logic in industrial automation and PLC programming.

In ladder logic — the most widely used PLC programming language and the foundation that the IEC 61131-3 standard formalises — File Fill is one of the building blocks that turns electrical-engineering reasoning into executable PLC code. Fills destination array with copies of single source value.

File Fill is evaluated as part of the PLC's deterministic scan: inputs are sampled, ladder rungs run in sequence, outputs are written, and the process repeats. File Fill sits inside that program-execution phase, where its specific logical or temporal behaviour shapes how the rung resolves.

Mastering File Fill is part of becoming productive in ladder logic — the language in which roughly 80% of industrial automation is still written. Visual readability is the reason ladder hasn't been displaced; engineers continue choosing it for binary logic and machine sequencing.