Comments - References - SIMATIC AX - Support documentation - ST Style Guide, Cheat sheet

Structured Text Style guide

Portfolio
SIMATIC AX
Product
SIMATIC AX
Software version
2510
Edition
02/2026
Language
English (original)
Package Name
@ax/st-styleguide

A distinction should be made between two types of comments:

  • Block comments (these describe what a function or a code section does)
  • Line comments (these describe the code of an individual line)

Recommendation:

A block comment should be located at the beginning of the corresponding code section. A line comment, if possible, should be located at the end of the code line – otherwise in front of the associated code line.

//Block comment that explains the next session of code
//It may be long and split into multiple lines to limit
//the number of columns

IF  Condition THEN //Line comment explaining a single line
    ;
END_IF;

Rule:

Comments in ST start with //. The comment is started after the slash symbols without any blanks. Reason: For test purposes, complete blocks can be simply removed using (* *) or /* */.

(* Code that's being temporarily deactivated for testing purposes
IF Condition THEN
    (*
    Multi-line
    comment in the wrong style
    *)

    //Multi-line
    //comment in the right style

    //statement that should not be active but is now
    //because of wrong use of multi line comments
    a := b;
END_IF;
*)