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### 5.1 KIND Type Parameters

The `KIND` type parameters supported by GNU Fortran for the primitive data types are:

`INTEGER`
  1, 2, 4, 8*, 16*, default: 4**
`LOGICAL`
  1, 2, 4, 8*, 16*, default: 4**
`REAL`
  4, 8, 10*, 16*, default: 4***
`COMPLEX`
  4, 8, 10*, 16*, default: 4***
`DOUBLE PRECISION`
  4, 8, 10*, 16*, default: 8***
`CHARACTER`
  1, 4, default: 1

* not available on all systems
** unless `-fdefault-integer-8` is used
*** unless `-fdefault-real-8` is used (see Fortran Dialect Options)

The `KIND` value matches the storage size in bytes, except for `COMPLEX` where the storage size is twice as much (or both real and imaginary part are a real value of the given size). It is recommended to use the SELECTED_CHAR_KIND, SELECTED_INT_KIND and SELECTED_REAL_KIND intrinsics or the `INT8`, `INT16`, `INT32`, `INT64`, `REAL32`, `REAL64`, and `REAL128` parameters of the `ISO_FORTRAN_ENV` module instead of the concrete values. The available kind parameters can be found in the constant arrays `CHARACTER_KINDS`, `INTEGER_KINDS`, `LOGICAL_KINDS` and `REAL_KINDS` in the ISO_FORTRAN_ENV module. For C interoperability, the kind parameters of the ISO_C_BINDING module should be used.