g95_quadmath/g95_quadmath.html

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      G95_QUADMATH - G95 Quadruple Real Precision
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      G95_QUADMATH <br> G95 Quadruple Real Precision
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    <p>
      <b>G95_QUADMATH</b> 
      is a FORTRAN90 program which
      illustrates the use of quadruple real precision arithmetic
      with the G95 compiler for FORTRAN.
    </p>

    <p>
      Every FORTRAN compiler offers a default real datatype as well as a double
      precision real data type.  
    </p>

    <p>
      Starting with FORTRAN90, it become possible to describe these types in terms
      of a KIND parameter.  The actual values of the KIND parameter corresponding
      to particular types was left up to the compiler writer.  For G95,
      real and double precision variables can be declared with KIND values of 4
      and 8 respectively:
      <blockquote><b>
        REAL ( KIND = 4 ) W<br>
        REAL ( KIND = 8 ) X
      </b></blockquote>
    </p>

    <p>
      On some systems, the G95 compiler provides a real data type stored in
      80 bytes, specified by a KIND value of 10, and on some systems, a data type
      stored in 128 bytes, with a KIND of 128.  Variable declarations would be
      <blockquote><b>
        REAL ( KIND = 10 ) Y<br>
        REAL ( KIND = 16 ) Z
      </b></blockquote>
    </p>

    <p>
      The Macintosh OSX system I have access to seems to have the KIND = 10 and KIND = 16
      options for the G95 compiler.
    </p>

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      Licensing:
    </h3>

    <p>
      The computer code and data files described and made available on this web page 
      are distributed under
      <a href = "../../txt/gnu_lgpl.txt">the GNU LGPL license.</a>
    </p>

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      Related Data and Programs:
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    <p>
      <a href = "../../f_src/g95_intrinsics/g95_intrinsics.html">
      G95_INTRINSICS</a>,
      a FORTRAN90 program which
      illustrates the use of intrinsic functions provided by the G95 compiler
      for FORTRAN.
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    <p>
      <a href = "../../f_src/gfortran_quadmath/gfortran_quadmath.html">
      GFORTRAN_QUADMATH</a>,
      a FORTRAN90 program which
      illustrates the use of quadruple precision real arithmetic
      provided by the Gnu GFORTRAN compiler for FORTRAN90.
    </p>

    <p>
      <a href = "../../f_src/real_precision/real_precision.html">
      REAL_PRECISION</a>,
      FORTRAN90 programs which
      investigate the somewhat awkward methods for requesting
      a real data type with given precision.  This is the preferred
      method for requesting double or quadruple precision arithmetic;
    </p>

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      Reference:
    </h3>

    <p>
      <ol>
        <li>
          The G95 home page,
          <a href = "http://www.g95.org/">
                     http://www.g95.org/</a>.
        </li>
      </ol>
    </p>

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      Examples and Tests:
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    <p>
      <ul>
        <li>
          <a href = "g95_quadmath.f90">g95_quadmath.f90</a>,
          a program that makes a simple test of the quadruple precision real arithmetic
          facility.
        </li>
        <li>
          <a href = "g95_quadmath.sh">g95_quadmath.sh</a>,
          commands that compile and run the test;
        </li>
        <li>
          <a href = "g95_quadmath_output.txt">
          g95_quadmath_output.txt</a>, 
          the output file;
        </li>
      </ul>
    </p>

    <p>
      You can go up one level to <a href = "../f_src.html">
      the FORTRAN90 source codes</a>.
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    <i>
      Last revised on 19 April 2011.
    </i>

    <!-- John Burkardt -->

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