The KIND type parameters supported by GNU Fortran for the primitive
data types are:
INTEGER1, 2, 4, 8*, 16*, default: 4**
LOGICAL1, 2, 4, 8*, 16*, default: 4**
REAL4, 8, 10*, 16*, default: 4***
COMPLEX4, 8, 10*, 16*, default: 4***
DOUBLE PRECISION4, 8, 10*, 16*, default: 8***
CHARACTER1, 4, default: 1
* not available on all systems
** unless -fdefault-integer-8 is used
*** unless -fdefault-real-8 is used (see Options controlling Fortran dialect)
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 — Choose character kind, SELECTED_INT_KIND — Choose integer kind and
SELECTED_REAL_KIND — Choose 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.