FORTRAN 77 Language Reference

## REAL*8 (Double-Precision Real) Constants

A double-precision constant is an approximation of a real number. It can be positive, negative, or zero. If no sign is present, the constant is assumed to be nonnegative. A double-precision constant has a double-precision exponent and an optional decimal point. Double-precision constants, REAL*8, use 8 bytes of storage. The REAL*8 notation is nonstandard. @

### Double-Precision Exponent

A double-precision exponent consists of the letter D, followed by an optional plus or minus sign, followed by an integer.

A double-precision exponent denotes a power of 10. The value of a double-precision constant is the product of that power of 10 and the constant that precedes the D. The form and interpretation are the same as for a real exponent, except that a D is used instead of an E.

Examples of double-precision constants are:

```1.6D-9
7D3
\$1.0D2.0 					Invalid-\$ not allowed, error message
82					Not DOUBLE PRECISION-need decimal point or exponent
29,002.0D0 					Invalid-comma not allowed, error message
1.8D308 					Invalid-too large, machine infinity is used
1.0D-324 					Invalid-too small, some precision is lost
```

The restrictions are:

• Other than the optional plus or minus sign, a decimal point, the digits 0 through 9, a blank, and the letter D. No other characters are allowed.

• The magnitude of an IEEE normalized double-precision floating-point value must be in the approximate range (2.225074D-308, 1.797693D+308).