Structured Text (ST), Extended Structured Text (ExST)

The ST Editor is used for programming POUs in the IEC-61131-3 programming language “Structured Text (ST)” or “Extended Structured Text”. “Extended Structured Text” offers certain additional functions, compared with the standard IEC 61131-3 language.

Structured Text is a programming language that is comparable to other high-level languages such as C or PASCAL, which enables the development of complex algorithms. The program code consists of a combination of expressions and instructions, which may be conditional (IF...THEN...ELSE) or looped (WHILE...DO).

An expression is a construct that returns a value after it was evaluated. Expressions can also be a combination of operators and operands. Assignments can also be used as expressions. An operand can be a constant, a variable, a function call or another expression.

Instructions control how the expressions are to be processed.

For this text editor various settings are available in the Options and Customize dialogs of the Tools menu with regard to behavior, appearance and menus. The familiar Windows functions (e.g. IntelliMouse) are also available for this editor.

ExST - Extended Structured Text

“Extended Structured Text (ExST)” is a TwinCAT-specific extension for “Structured Text (ST)”, as defined in the IEC 61131-3 standard.

See also:

Further Information