Q exponent-letter ¶GNU Fortran accepts real literal constants with an exponent-letter
of Q, for example, 1.23Q45. The constant is interpreted
as a REAL(16) entity on targets that support this type. If
the target does not support REAL(16) but has a REAL(10)
type, then the real-literal-constant will be interpreted as a
REAL(10) entity. In the absence of REAL(16) and
REAL(10), an error will occur.