Data type 'REAL' / 'LREAL'

The data types ‎REAL‎ and ‎LREAL‎ are floating-point types according to IEEE 754. They are necessary when using decimal numbers and floating-point numbers in decimal notation or exponential notation.

Example

PROGRAM PLC_PRG
VAR
	rMax: REAL := 3.402823E+38; // Largest number
	rPosMin : REAL := 1.0E-44; // Smallest positive number
	rNegMax: REAL := -1.0E-44; // Largest negative number
	rMin: REAL := -3.402823E+38; // Smallest number

	lrMax: LREAL := 1.7976931348623157E+308; // Largest number
	lrPosMin : LREAL := 4.94065645841247E-324; // Smallest positve number
	lNegMax: LREAL := -4.94065645841247E-324; // Largest negative number
	lrMin: LREAL := -1.7976931348623157E+308; // Smallest number
END_VAR

NOTICE

Support for the ‎LREAL‎ data type depends on the target device in use. Refer to the respective documentation as to whether or not the 64-bit type ‎LREAL‎ is converted to ‎REAL‎ or remains as ‎LREAL‎ when compiling the application. Conversion may result in the loss of information.

NOTICE

If the value of the ‎REAL‎/‎LREAL‎ number is outside of the value range of the integer, then an undefined result is yielded from a data type conversion from ‎REAL‎ or ‎LREAL‎ to ‎SINT‎, ‎USINT‎, ‎INT‎, ‎UINT‎, ‎DINT‎, ‎UDINT‎, ‎LINT‎, or ‎ULINT‎. The result depends on the target system. An exception error is also possible. To get code that is independent of the target system, the application must catch value range violations.

If the ‎REAL‎/‎LREAL‎ number is within the value range of the integer data type, then the conversion operates the same way on all systems.