REAL(8) (same as REAL(KIND=8)) data occupies 8 contiguous bytes stored in IEEE T_floating format. Bits are labeled from the right, 0 through 63, as shown below.
The form of REAL(8) data is sign magnitude, with bit 63 the sign bit (0 for positive numbers, 1 for negative numbers), bits 62:52 a binary exponent in excess 1023 notation, and bits 51:0 a normalized 53-bit fraction including the redundant most-significant fraction bit not represented.
The value of data is in the approximate range: 2.2250738585072013D-308 (normalized) to 1.7976931348623158D308. The IEEE denormalized (subnormal) limit is 4.94065645841246544D-324. The precision is approximately one part in 2**52; typically 15 decimal digits.