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Next: <a href="Derived-Types-and-struct.html#Derived-Types-and-struct" accesskey="n" rel="next">Derived Types and struct</a>, Up: <a href="Interoperability-with-C.html#Interoperability-with-C" accesskey="u" rel="up">Interoperability with C</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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<a name="Intrinsic-Types-1"></a>
<h4 class="subsection">7.1.1 Intrinsic Types</h4>

<p>In order to ensure that exactly the same variable type and kind is used
in C and Fortran, the named constants shall be used which are defined in the
<code>ISO_C_BINDING</code> intrinsic module.  That module contains named constants
for kind parameters and character named constants for the escape sequences
in C.  For a list of the constants, see <a href="ISO_005fC_005fBINDING.html#ISO_005fC_005fBINDING">ISO_C_BINDING</a>.
</p>
<p>For logical types, please note that the Fortran standard only guarantees
interoperability between C99&rsquo;s <code>_Bool</code> and Fortran&rsquo;s <code>C_Bool</code>-kind
logicals and C99 defines that <code>true</code> has the value 1 and <code>false</code>
the value 0.  Using any other integer value with GNU Fortran&rsquo;s <code>LOGICAL</code>
(with any kind parameter) gives an undefined result.  (Passing other integer
values than 0 and 1 to GCC&rsquo;s <code>_Bool</code> is also undefined, unless the
integer is explicitly or implicitly casted to <code>_Bool</code>.)
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