The following strings are reserved as keywords, i.e. they cannot be used as identifiers for variables or POUs:
ABS ⮫ “ABS”
ACOS ⮫ “ACOS”
ACTION (only used in the Export Format)
ADD ⮫ “ADD”
ADR ⮫ “ADR”
ADRINST ⮫ “ADRINST”
AND ⮫ “AND”
ANDN
ARRAY ⮫ “ARRAY”
ASIN ⮫ “ASIN”
AT ⮫ “Address”
ATAN ⮫ “ATAN”
BITADR ⮫ “BITADR”
BOOL ⮫ “BOOL”
BY ⮫ “FOR loop”
CAL
CALC
CALCN
CASE ⮫ “CASE instruction”
CONSTANT ⮫ “Constants, typed literals”
COS ⮫ “COS”
DATE ⮫ “Time data types”
DIV ⮫ “DIV”
DO ⮫ “FOR loop”
DWORD ⮫ “Integer data types”
ELSE ⮫ “IF instruction”
ELSEIF ⮫ “IF instruction”
END_ACTION (only used in the Export Format)
END_CASE ⮫ “CASE instruction”
END_FOR ⮫ “FOR loop”
END_FUNCTION (only used in the Export Format)
END_FUNCTION_BLOCK (only used in the Export Format)
END_IF ⮫ “IF instruction”
END_PROGRAM (only used in the Export Format)
END_REPEAT ⮫ “REPEAT loop”
END_STRUCT ⮫ “Structures”
END_TYPE ⮫ “Enumeration”
END_VAR ⮫ “Local variables”
END_WHILE ⮫ “WHILE loop”
EQ ⮫ “EQ”
EXIT ⮫ “EXIT instruction”
EXP ⮫ “EXP”
EXPT ⮫ “EXPT”
FALSE ⮫ “BOOL”
FOR ⮫ “FOR loop”
FUNCTION ⮫ “Function”
FUNCTION_BLOCK ⮫ “Function block”
GE ⮫ “GE”
GT ⮫ “GT”
INDEXOF ⮫ “INDEXOF”
INI ⮫ “INI operator”
JMP
JMPC
JMPCN
LD
LDN
LE ⮫ “LE”
LN ⮫ “LN”
LOG ⮫ “LOG”
LREAL ⮫ “REAL / LREAL”
LT ⮫ “LT”
LWORD ⮫ “Integer data types”
MAX ⮫ “MAX”
MIN ⮫ “MIN”
MOD ⮫ “MOD”
MOVE ⮫ “MOVE”
MUL ⮫ “MUL”
MUX ⮫ “MUX”
NE ⮫ “NE”
NOT ⮫ “NOT”
OF ⮫ “ARRAY”
OR ⮫ “OR”
ORN
PERSISTENT
POINTER ⮫ “Pointer”
PROGRAM ⮫ “Program”
R
READ_ONLY
READ_WRITE
REAL ⮫ “REAL / LREAL”
REPEAT ⮫ “REPEAT loop”
RET
RETAIN
RETC
RETCN
RETURN ⮫ “RETURN instruction”
ROL ⮫ “ROL”
ROR ⮫ “ROR”
S
SEL ⮫ “SEL”
SHL ⮫ “SHL”
SHR ⮫ “SHR”
SIN ⮫ “SIN”
SIZEOF ⮫ “SIZEOF”
SQRT ⮫ “SQRT”
ST
STN
STRING ⮫ “STRING”
STRUCT ⮫ “Structures”
SUB ⮫ “SUB”
TAN ⮫ “TAN”
THEN ⮫ “IF instruction”
TIME ⮫ “Time data types”
TO ⮫ “FOR loop”
TRUE ⮫ “BOOL”
TRUNC ⮫ “TRUNC”
TYPE ⮫ “Enumeration”
UDINT ⮫ “Integer data types”
ULINT ⮫ “Integer data types”
UNTIL ⮫ “REPEAT loop”
USINT ⮫ “Integer data types”
VAR_ACCESS (only used very specifically, depending on the hardware)
VAR_CONFIG ⮫ “Overview”
VAR_CONSTANT ⮫ “Constants, typed literals”
VAR_EXTERNAL ⮫ “External variables”
VAR_GLOBAL ⮫ “Several variables lists”
VAR_IN_OUT ⮫ “Input and output variables”
VAR_INPUT ⮫ “Input variable”
VAR_OUTPUT ⮫ “Output variable”
WHILE ⮫ “WHILE loop”
WSTRING (IEC data type is not supported)
XOR ⮫ “XOR”
XORN
Additionally all conversion operators as listed in the 'Edit' 'Input assistant' are handled as keywords.