The REAL4 keyword denotes a single precision 32 bit number with values ranging from negative 3.402823e38 to positive 3.402823e38, as well as positive or negative zero, PositiveInfinity, NegativeInfinity, and not a number ( NaN). It is intended to represent values that are extremely large (such as distances between planets or galaxies) or extremely small (such as the molecular mass of a substance in kilograms) and that often are imprecise (such as the distance from earth to another solar system). The REAL4 type complies with the IEC 60559:1989 (IEEE 754) standard for binary floating-point arithmetic.
