General

CODESYS V3 supports all IEC-61131-3 operators. These operators are recognized implicitly throughout the project. In addition to these IEC operators, CODESYS also supports some non-IEC 61131-3 operators.

Operators are used in blocks, such as functions.

For information about the processing order (binding strength) of the ST operators, please refer to the section on ST expressions.

CAUTION

For operations with floating-point data types, the computational result depends on the applied target system hardware.

CAUTION

For operations with overflow or underflow in the data type, the computational result depends on the applied target system hardware.

Overflow/underflow in the data type

The CODESYS compiler generates code for the target device and computes temporary results always with the native size that is defined by the target device. For example, computation is performed at least with 32-bit temporary values on x86 and ARM systems and always with 64-bit temporary values on x64 systems. This provides considerable advantages in the computation speed and often also produces the desired result. But this also means that an overflow or underflow in the data type is not truncated in some cases.

Examples

Example 1

The result of this addition is not truncated and the result in ‎dwVar‎ is ‎65536‎.

VAR
wVar : WORD;
dwVar: DWORD;
END_VAR

wVar := 65535;
dwVar := wVar + 1;

Example 2

The overflow and underflow in the data type is not truncated and the results (‎bVar1, bVar2‎) of both comparisons are ‎FALSE‎ on 32-bit and 64-bit hardware.

VAR
wVar1 : WORD;
wVar2 : WORD;
bVar1 : BOOL;
bVar2 : BOOL;
END_VAR

wVar1 := 65535;
wVar2 := 0;
bVar1 := (wVar1 + 1) = wVar2;
bVar2 := (wVar2 - 1) = wVar1;

Example 3

By the assignment to ‎wVar3‎, the value is truncated to the target data type ‎WORD‎ and the result ‎bvar1‎ is ‎TRUE‎.

VAR
wVar1 : WORD;
wVar2 : WORD;
wVar3 : WORD;
bVar1 : BOOL;
END_VAR

wVar1 := 65535;
wVar2 := 0; 
wVar3 := (wVar1 + 1);
bVar1 := wVar3 = wVar2;

Example 4

In order to force the compiler to truncate the temporary results, a conversion can be inserted.

The type conversion makes sure that both comparisons are 16-bit only and the results (‎bVar1, bVar2‎) of both comparisons are each ‎TRUE‎.

VAR
wVar1 : WORD;
wVar2 : WORD;
bVar1 : BOOL;
bVar2 : BOOL;
END_VAR

wVar1 := 65535;
wVar2 := 0;
bVar1 := TO_WORD(wVar1 + 1) = wVar2;
bVar2 := TO_WORD(wVar2 - 1) = wVar1;

Arithmetic operators

⮫ “Operator 'INDEXOF'”

⮫ “Operator 'SIZEOF'”

⮫ “Operator 'XSIZEOF'”

Bitstring operators

⮫ “Operator 'AND_THEN'”

⮫ “Operator 'OR_ELSE'”

Bitshift operators

Selection operators

Comparison operators

A comparison operator is a Boolean that compares two inputs (first and second operand).

Address operators

⮫ “Operator 'Content Operator'”

⮫ “Operator 'BITADR'”

Call operators

⮫ “Operator 'CAL'”

Type conversion operators

You can explicitly call type conversion operators. The type conversion operators described below are available for typed conversions from one elementary type to another elementary type, as well as for overloading. Conversions from a larger type to a smaller type are also implicitly possible (for example, from ‎INT‎ to ‎BYTE‎ or from ‎DINT‎ to ‎WORD‎).

Typed conversion: ‎<elementary data type> _TO_ <another elementary data type>‎

Overloaded conversion: ‎TO_ <elementary data type>‎

Elementary data types:

<elementary  data type> = 
__UXINT | __XINT | __XWORD | BIT | BOOL | BYTE | DATE | DATE_AND_TIME | DINT | DT | DWORD | INT | LDATE | LDATE_AND_TIME | LDT | LINT | LREAL | LTIME | LTOD | LWORD | REAL | SINT | TIME | TOD | UDINT | UINT | ULINT | USINT | WORD

The keywords ‎T‎, ‎TIME_OF_DAY‎ and ‎DATE_AND_TIME‎ are alternative forms for the data types ‎TIME‎, ‎TOD‎, and ‎DT‎. ‎T‎, ‎TIME_OF_DAY‎ and ‎DATE_AND_TIME‎ are not represented as a type conversion command.

NOTICE

If the operand value for a type conversion operator is outside of the value range of the target data type, then the result output depends on the processor type and is therefore undefined. This is the case, for example, when a negative operand value is converted from ‎LREAL‎ to the target data type ‎UINT‎.

Information can be lost when converting from larger data types to smaller data types.

NOTICE

String manipulation when converting to ‎STRING‎ or ‎WSTRING‎

When converting the type to ‎STRING‎ or ‎WSTRING‎, the typed value is left-aligned as a character string and truncated if it is too long. Therefore, declare the return variable for the type conversion operators ‎<>_TO_STRING‎ and ‎<>_TO_WSTRING‎ long enough that the character string has enough space without any manipulation.