REAL_8

 DOUBLE PRECISION (REAL(KIND=8) or REAL*8)

 A DOUBLE PRECISION constant has more than twice the accuracy of a
 REAL number, and greater range.

 A 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.

 Either VAX D_floating, G_floating, or IEEE T_floating format is
 used, depending on the compiler option specified.