Named Constants

Intrinsic-Type Constants

The following table shows interoperable Fortran types and C Types.

Fortran Type	Named Constant for the KIND	C Type
INTEGER	C_INT	int
	C_SHORT	short int
	C_LONG	long int
	C_LONG_LONG	long long int
	C_SIGNED_CHAR	signed char, unsigned char
	C_SIZE_T	size_t
	C_INT8_T	int8_t
	C_INT16_T	int16_t
	C_INT32_T	int32_t
	C_INT64_T	int64_t
	C_INT_LEAST8_T	int_least8_t
	C_INT_LEAST16_T	int_least16_t
	C_INT_LEAST32_T	int_least32_t
	C_INT_LEAST64_T	int_least64_t
	C_INT_FAST8_T	int_fast8_t
	C_INT_FAST16_T	int_fast16_t
	C_INT_FAST32_T	int_fast32_t
	C_INT_FAST64_T	int_fast64_t
	C_INTMAX_T	intmax_t
	C_INTPTR_T	intptr_t
REAL	C_FLOAT	float
	C_DOUBLE	double
	C_LONG_DOUBLE	long double
COMPLEX	C_FLOAT_COMPLEX	float _Complex
	C_DOUBLE_COMPLEX	double _Complex
	C_LONG_DOUBLE_COMPLEX	long double _Complex
LOGICAL¹	C_BOOL	_Bool
CHARACTER²	C_CHAR	char
¹ Use compiler option fpscomp logicals so that .TRUE. is 1 and .FALSE. is 0 as defined for C's _Bool. ²For character type, the length type parameter must be omitted or it must be specified by an initialization expression whose value is one.

For example, an integer type with the kind type parameter C_LONG is interoperable with the C integer type "long" or any C type derived from "long".

The value of C_INT will be a valid value for an integer kind type parameter on the processor. The values for the other integer named constants (C_INT*) will be a valid value for an integer kind type parameter on the processor, if any, or one of the following:

-1 if the C processor defines the corresponding C type and there is no interoperating Fortran processor kind
-2 if the C processor does not define the corresponding C type

The values of C_FLOAT, C_DOUBLE, and C_LONGDOUBLE will be a valid value for a real kind type parameter on the processor, if any, or one of the following:

-1 if the C processor's type does not have a precision equal to the precision of any of the Fortran processor's real kinds
-2 if the C processor's type does not have a range equal to the range of any of the Fortran processor's real kinds
-3 if the C processor's type has neither the precision or range equal to the precision or range of any of the Fortran processor's real kinds
-4 if there is no interoperating Fortran processor or kind for other reasons

The values of C_FLOAT_COMPLEX, C_DOUBLE_COMPLEX, and C_LONG_DOUBLE_COMPLEX will be the same as those of C_FLOAT, C_DOUBLE, and C_LONG_DOUBLE, respectively.

The value of C_BOOL will be a valid value for a logical kind parameter on the processor, if any, or -1.

The value of C_CHAR is the character kind.

Character Constants

The following table shows interoperable named constants and C characters:

Fortran Named Constant	Definition	C Character
C_NULL_CHAR	null character	'\0'
C_ALERT	alert	'\a'
C_BACKSPACE	backspace	'\b'
C_FORM_FEED	form feed	'\f'
C_NEW_LINE	new line	'\n'
C_CARRIAGE_RETURN	carriage return	'\r'
C_HORIZONTAL_TAB	horizontal tab	'\t'
C_VERTICAL_TAB	vertical tab	'\v'

Derived-Type Constants

The constant C_NULL_PTR is of type C_PTR; it has the value of a C null data pointer. The constant C_NULL_FUNPTR is of type C_FUNPTR; it has the value of a C null function pointer.