→IEC-identifier

an identifier according to →IEC-standardcombination of letters, numbers, and underscore characters which begins with a letter or underscore and which names a language element; The case of letters shall not be significant in identifiers, for example, the identifiers abcdABCD, and aBCd shall be interpreted identically. The underscore character shall be significant in identifiers, for example, A_BCD and AB_CD shall be interpreted as different identifiers. Multiple leading or multiple embedded underlines are not allowed; for example, the character sequences __LIM_SW5 and LIM__SW5 are not valid identifiers. Trailing underscores are not allowed; for example, the character sequence LIM_SW5_ is not a valid identifier.

Identifiers in the ST-code, FBD-logic or the ladder diagram must not be →keywords according to the IEC-standard, see "Reserved keywords".

Identifiers in the library configuration must not be →keywords for the library configuration, see "Reserved keywords in the library configuration"

Identifiers in the ST-code, FBD-logic or ladder diagram must not contain special characters, such as umlauts (äöü) or ß.