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.
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).