### 3.1.2.3 REAL(8) or DOUBLE PRECISION Constants

A REAL(8) or DOUBLE PRECISION constant has more than twice the accuracy of a REAL(4) number, and greater range.

A REAL(8) or DOUBLE PRECISION constant occupies eight bytes of memory. The number of digits that precede the exponent is unlimited, but typically only the leftmost 15 digits are significant.

On Tru64 UNIX, Linux, WNT, and W9* systems, IEEE T_floating format is used. On OpenVMS systems, either Compaq VAX D_floating, G_floating, or IEEE T_floating format is used, depending on the compiler option specified.

Examples

The following examples show valid and invalid REAL(8) or DOUBLE PRECISION constants:

Valid |
`123456789D+5` |
`123456789E+5_8` |
`+2.7843D00` |
`-.522D-12` |
`2E200_8` |
`2.3_8` |
`3.4E7_8` |
Invalid | Explanation
`-.25D0_2` | 2 is not a valid kind for reals.
`+2.7182812846182` | No D exponent designator is present; this is a valid single-precision constant.
`1234567890D45` | Too large for D_floating format; valid for G_floating and T_floating format.
`123456789.D400` | Too large for any double-precision format.
`123456789.D-400` | Too small for any double-precision format.

For More Information:

- On general rules for real constants, see Section 3.1.2.1.
- On the format and range of DOUBLE PRECISION (REAL(8)) data, see your user manual or programmer's guide.
- On compiler options affecting DOUBLE PRECISION data, see your user manual or programmer's guide.

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