An expression is a construct that returns a value following its evaluation.

Expressions are composed of operators and operands. In Extended Structured Text (ExST) you can also use assignments as expressions. An operand can be a constant, a variable, a function call or a further expression.

Evaluation of expressions

The evaluation of an expression takes place by processing the operators according to certain rules of binding. CODESYS processes the operator with the strongest binding first. Operators with the same binding strength are processed from left to right.