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<title>The GNU Fortran Compiler: Introduction to Intrinsics</title>

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<a name="Introduction-to-Intrinsics"></a>
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<a name="Introduction-to-intrinsic-procedures"></a>
<h3 class="section">9.1 Introduction to intrinsic procedures</h3>

<p>The intrinsic procedures provided by GNU Fortran include all of the
intrinsic procedures required by the Fortran 95 standard, a set of
intrinsic procedures for backwards compatibility with G77, and a
selection of intrinsic procedures from the Fortran 2003 and Fortran 2008
standards.  Any conflict between a description here and a description in
either the Fortran 95 standard, the Fortran 2003 standard or the Fortran
2008 standard is unintentional, and the standard(s) should be considered
authoritative.
</p>
<p>The enumeration of the <code>KIND</code> type parameter is processor defined in
the Fortran 95 standard.  GNU Fortran defines the default integer type and
default real type by <code>INTEGER(KIND=4)</code> and <code>REAL(KIND=4)</code>,
respectively.  The standard mandates that both data types shall have
another kind, which have more precision.  On typical target architectures
supported by <code>gfortran</code>, this kind type parameter is <code>KIND=8</code>.
Hence, <code>REAL(KIND=8)</code> and <code>DOUBLE PRECISION</code> are equivalent.
In the description of generic intrinsic procedures, the kind type parameter
will be specified by <code>KIND=*</code>, and in the description of specific
names for an intrinsic procedure the kind type parameter will be explicitly
given (e.g., <code>REAL(KIND=4)</code> or <code>REAL(KIND=8)</code>).  Finally, for
brevity the optional <code>KIND=</code> syntax will be omitted.
</p>
<p>Many of the intrinsic procedures take one or more optional arguments.
This document follows the convention used in the Fortran 95 standard,
and denotes such arguments by square brackets.
</p>
<p>GNU Fortran offers the <samp>-std=f95</samp> and <samp>-std=gnu</samp> options,
which can be used to restrict the set of intrinsic procedures to a 
given standard.  By default, <code>gfortran</code> sets the <samp>-std=gnu</samp>
option, and so all intrinsic procedures described here are accepted.  There
is one caveat.  For a select group of intrinsic procedures, <code>g77</code>
implemented both a function and a subroutine.  Both classes 
have been implemented in <code>gfortran</code> for backwards compatibility
with <code>g77</code>.  It is noted here that these functions and subroutines
cannot be intermixed in a given subprogram.  In the descriptions that follow,
the applicable standard for each intrinsic procedure is noted.
</p>


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