Loose variables turn into a mess quickly. Group the ones that belong together into a named shape, a STRUCT, and your code starts to read like the machine it controls.
A bottling line has a recipe with a fill volume, a cap torque and a label flag. You can hold that as three loose variables or as one tidy ST_Recipe. Edit the fields and the Structured Text updates to match.
💡 Now Line1.recipe is one variable you can pass around, copy, or store as an array of recipes, where before you had three to juggle. Add a field to the type and every recipe gets it for free.
ENUM: readable states
Instead of "mode = 2", say what you mean. Click a mode:
UNION: one memory, two views
TYPE U_Word : UNION asWord : WORD; // all 16 bits asBytes : ARRAY[0..1] OF BYTE; END_UNION END_TYPE
Both members share the same bytes. Write asWord and read asBytes[0], which is handy for decoding a fieldbus register without bit-shifting by hand.
You write to myWord.asWord. What happens to myWord.asBytes?