gcc/fortran/doc/gfortran/compiler-characteristics/kind-type-parameters.rst

   1 ..
   2   Copyright 1988-2022 Free Software Foundation, Inc.
   3   This is part of the GCC manual.
   4   For copying conditions, see the copyright.rst file.
   5
   6 .. index:: kind
   7
   8 .. _kind-type-parameters:
   9
  10 KIND Type Parameters
  11 ********************
  12
  13 The ``KIND`` type parameters supported by GNU Fortran for the primitive
  14 data types are:
  15
  16 ``INTEGER``
  17
  18   1, 2, 4, 8 [#f1]_, 16 [#f1]_, default: 4 [#f2]_
  19
  20 ``LOGICAL``
  21
  22   1, 2, 4, 8 [#f1]_, 16 [#f1]_, default: 4 [#f2]_
  23
  24 ``REAL``
  25
  26   4, 8, 10 [#f1]_, 16 [#f1]_, default: 4 [#f3]_
  27
  28 ``COMPLEX``
  29
  30   4, 8, 10 [#f1]_, 16 [#f1]_, default: 4 [#f3]_
  31
  32 ``DOUBLE PRECISION``
  33
  34   4, 8, 10 [#f1]_, 16 [#f1]_, default: 8 [#f3]_
  35
  36 ``CHARACTER``
  37
  38   1, 4, default: 1
  39
  40 .. [#f1] not available on all systems
  41 .. [#f2] unless :option:`-fdefault-integer-8` is used
  42 .. [#f3] unless :option:`-fdefault-real-8` is used (see :ref:`fortran-dialect-options`)
  43
  44 The ``KIND`` value matches the storage size in bytes, except for
  45 ``COMPLEX`` where the storage size is twice as much (or both real and
  46 imaginary part are a real value of the given size).  It is recommended to use
  47 the :ref:`SELECTED_CHAR_KIND`, :ref:`SELECTED_INT_KIND` and
  48 :ref:`SELECTED_REAL_KIND` intrinsics or the ``INT8``, ``INT16``,
  49 ``INT32``, ``INT64``, ``REAL32``, ``REAL64``, and ``REAL128``
  50 parameters of the ``ISO_FORTRAN_ENV`` module instead of the concrete values.
  51 The available kind parameters can be found in the constant arrays
  52 ``CHARACTER_KINDS``, ``INTEGER_KINDS``, ``LOGICAL_KINDS`` and
  53 ``REAL_KINDS`` in the :ref:`ISO_FORTRAN_ENV` module.  For C interoperability,
  54 the kind parameters of the :ref:`ISO_C_BINDING` module should be used.