SIZEOF

The operator is an extension of the IEC 61131-3 standard.

The operator is used to determine the number of bytes required by the specified variable x. The SIZEOF operator always returns an unsigned value. The type of the return variable adapts to the detected size of variable x.

Syntax:

<return value> := SIZEOF( <variable name> | <date type name> );

Return value of SIZEOF(x) (`<return value>)`	Data type of the constant, which TwinCAT implicitly uses for the size that was found.
0 <= size of x < 256	USINT
256 <= size of x < 65536	UINT
65536 <= size of x < 4294967296	UDINT
4294967296 <= size of x	ULINT

Sample:

PROGRAM MAIN
VAR
    aArr1 : ARRAY[0..4] OF INT; 
    nSize : INT;
END_VAR

nSize := SIZEOF(aArr1);

Result:

nSize = 10.

	When assigning to a type __UXINT variable, you should use the XSIZEOF operator instead of the SIZEOF operator. This is because with XSIZEOF the data type of the return value depends on the platform. As a result, problems that occur when using the SIZEOF operator do not occur.