Glossary · IF
What is IF statement?
The conditional in ST: IF ... THEN ... ELSIF ... ELSE ... END_IF. The most used statement in the language.
Branches are tested in order and only the first true one runs. It must be closed with END_IF, and forgetting that is a classic beginner error.
When the result is a single boolean, a direct assignment is clearer than a conditional: write Alarm := Level > 85.0; instead of IF Level > 85.0 THEN Alarm := TRUE; ELSE Alarm := FALSE; END_IF.
Related terms
- CASE statement
- A selection statement that runs one branch depending on an integer or enumerated value. It is what state machines in ST are built from.
- Boolean expression
- An expression whose result is TRUE or FALSE, built from comparisons and the operators AND, OR, XOR and NOT.