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In all editors, you must capitalize keywords that for example denote scopes, data types, or operators. Keywords cannot be used as variable names.

Example 

VAR
END_VAR
BOOL_TO_INT
IF
THEN
ELSE
LTIME
MUL
XOR
PERSISTENT
PROGRAM

CODESYS checks the correct use of keywords automatically and highlights errors immediately during input with a wavy underline.

When CODESYS creates implicit code, variables and functions are generally given a name that is prepended with two underscores "__". The use of double underscores in the implementation code is prevented automatically. This eliminates conflicts between internal system identifiers and identifiers assigned by the programmer.

The following keywords are used in the CODESYS export format. Therefore, you may not use them as identifiers:

  • ‎ACTION‎

  • ‎END_ACTION‎

  • ‎END_FUNCTION‎

  • ‎END_FUNCTION_BLOCK‎

  • ‎END_PROGRAM‎

Other valid keywords:

  • ‎VAR_ACCESS‎

  • ‎READ_ONLY‎

  • ‎READ_WRITE‎

  • ‎PARAMS‎