#### 6.1.8 `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.