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<title>The GNU Fortran Compiler: Hollerith constants support</title>

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<a name="Hollerith-constants-support"></a>
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<a name="Hollerith-constants-support-1"></a>
<h4 class="subsection">6.1.13 Hollerith constants support</h4>
<a name="index-Hollerith-constants"></a>

<p>GNU Fortran supports Hollerith constants in assignments, function
arguments, and <code>DATA</code> and <code>ASSIGN</code> statements.  A Hollerith
constant is written as a string of characters preceded by an integer
constant indicating the character count, and the letter <code>H</code> or
<code>h</code>, and stored in bytewise fashion in a numeric (<code>INTEGER</code>,
<code>REAL</code>, or <code>complex</code>) or <code>LOGICAL</code> variable.  The
constant will be padded or truncated to fit the size of the variable in
which it is stored.
</p>
<p>Examples of valid uses of Hollerith constants:
</p><div class="smallexample">
<pre class="smallexample">      complex*16 x(2)
      data x /16Habcdefghijklmnop, 16Hqrstuvwxyz012345/
      x(1) = 16HABCDEFGHIJKLMNOP
      call foo (4h abc)
</pre></div>

<p>Invalid Hollerith constants examples:
</p><div class="smallexample">
<pre class="smallexample">      integer*4 a
      a = 8H12345678 ! Valid, but the Hollerith constant will be truncated.
      a = 0H         ! At least one character is needed.
</pre></div>

<p>In general, Hollerith constants were used to provide a rudimentary
facility for handling character strings in early Fortran compilers,
prior to the introduction of <code>CHARACTER</code> variables in Fortran 77;
in those cases, the standard-compliant equivalent is to convert the
program to use proper character strings.  On occasion, there may be a
case where the intent is specifically to initialize a numeric variable
with a given byte sequence.  In these cases, the same result can be
obtained by using the <code>TRANSFER</code> statement, as in this example.
</p><div class="smallexample">
<pre class="smallexample">      INTEGER(KIND=4) :: a
      a = TRANSFER (&quot;abcd&quot;, a)     ! equivalent to: a = 4Habcd
</pre></div>


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