Data Types

Data types are defined within the common elements of IEC International Electrotechnical Commission - A not-for-profit, non-governmental international standards organization that prepares and publishes International Standards for all electrical, electronic and related technologies. 61131-3.

Why Data Typing?

Data typing is implemented to define the type of any parameter used. This helps prevent errors early on in the programming The act of performing a sequence of instructions or commands. phase (e.g., avoids dividing a Date by an Integer).

When you have defined whether the data is a string, a date, an integer or a 16-bit Boolean input, there is no longer any confusion, nor any conflict between different people using the textual representation (i.e., the name of the variable).

Different Data Types

Common Data Types: Boolean, Byte, Date, Integer, Real, String, Time_of_Day, Word.
Derived Data Types: Define personal data types based on the Common data types.
- Example: Define an analog input channel as a data type and re-use it.

List of Data Types

Type	Prefix	Description	Values
BOOL		Boolean (bit)	FALSE, TRUE Stored in 1 byte.
BYTE		Same as USINT.
DINT		Signed double precision integer in 32-bits.	-2147483648 to 2147483647
DWORD		Same as UDINT.
INT	INT#	Signed integer in 16-bits.	-32768 to +32767
LINT	LINT#	Long signed integer in 64-bits.
LREAL^‡	LREAL#	Double precision floating point stored in 64-bits.	-1.7E308 to 1.7E308 14 to 15 significant digits of accuracy Accuracy is the distance between the actual position of a mechanical system and the expected position. It is typically specified in microns or arcsec per given travel for a deviation of ±3 (sigma).
LWORD		Same as ULINT.
REAL^‡	REAL# ^‡‡	Single precision floating point stored in 32-bits.	-3.4E38 to 3.4E38 6 to 7 significant digits of accuracy.
SINT	SINT#	Small signed integer in 8-bits.	-128 to +127
STRING		Variable length string with declared maximum length. Each character is store on 1 byte (i.e., on 8-bits).	Maximum length cannot exceed 255 characters.
TIME	T# or TIME#	Time data type is used to specify a time variable. Accuracy is 1ms. See TIME.	0ms - 24hr
UDINT	UDINT#	Unsigned integer in 32-bits.	0 to +4294967295
UINT	UINT#	Unsigned integer in 16-bits.	0 to 65535
ULINT	ULINT#	Long unsigned integer in 64-bits.
USINT	USINT#	Small unsigned integer in 8-bits.	0 to 255
WORD		Same as UINT.
WSTRING		Do not use! The WSTRING is not supported.

‡ REAL variables are limited to 6 digits of accuracy.
To achieve greater accuracy, a longer mantissa may be specified by prefixing LREAL with #.

Example: To achieve an accuracy of 20 digits for the value of Pi, rather than what REAL provides (3.14159), set the type to LREAL#3.141592653589793238.

‡‡ REAL is restrictive, but because it is the default, it is recommended to explicitly declare real constants with the LREAL# prefix.

Use 2#, 8#, or 16# prefixes to specify an integer in binary, octal or hexadecimal basis, respectively.