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+<p>
+Next: <a href="Asynchronous-I_002fO.html#Asynchronous-I_002fO" accesskey="n" rel="next">Asynchronous I/O</a>, Previous: <a href="File-operations-on-symbolic-links.html#File-operations-on-symbolic-links" accesskey="p" rel="previous">File operations on symbolic links</a>, Up: <a href="Compiler-Characteristics.html#Compiler-Characteristics" accesskey="u" rel="up">Compiler Characteristics</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>
+</div>
+<hr>
+<a name="File-format-of-unformatted-sequential-files-1"></a>
+<h3 class="section">4.9 File format of unformatted sequential files</h3>
+<a name="index-file_002c-unformatted-sequential"></a>
+<a name="index-unformatted-sequential"></a>
+<a name="index-sequential_002c-unformatted"></a>
+<a name="index-record-marker"></a>
+<a name="index-subrecord"></a>
+
+<p>Unformatted sequential files are stored as logical records using
+record markers.  Each logical record consists of one of more
+subrecords.
+</p>
+<p>Each subrecord consists of a leading record marker, the data written
+by the user program, and a trailing record marker.  The record markers
+are four-byte integers by default, and eight-byte integers if the
+<samp>-fmax-subrecord-length=8</samp> option (which exists for backwards
+compability only) is in effect.
+</p>
+<p>The representation of the record markers is that of unformatted files
+given with the <samp>-fconvert</samp> option, the <a href="CONVERT-specifier.html#CONVERT-specifier">CONVERT specifier</a>
+in an open statement or the <a href="GFORTRAN_005fCONVERT_005fUNIT.html#GFORTRAN_005fCONVERT_005fUNIT">GFORTRAN_CONVERT_UNIT</a> environment
+variable.
+</p>
+<p>The maximum number of bytes of user data in a subrecord is 2147483639
+(2 GiB - 9) for a four-byte record marker.  This limit can be lowered
+with the <samp>-fmax-subrecord-length</samp> option, although this is
+rarely useful. If the length of a logical record exceeds this limit,
+the data is distributed among several subrecords.
+</p>
+<p>The absolute of the number stored in the record markers is the number
+of bytes of user data in the corresponding subrecord.  If the leading
+record marker of a subrecord contains a negative number, another
+subrecord follows the current one.  If the trailing record marker
+contains a negative number, then there is a preceding subrecord.
+</p>
+<p>In the most simple case, with only one subrecord per logical record,
+both record markers contain the number of bytes of user data in the
+record.
+</p>
+<p>The format for unformatted sequential data can be duplicated using
+unformatted stream, as shown in the example program for an unformatted
+record containing a single subrecord:
+</p>
+<div class="smallexample">
+<pre class="smallexample">program main
+  use iso_fortran_env, only: int32
+  implicit none
+  integer(int32) :: i
+  real, dimension(10) :: a, b
+  call random_number(a)
+  open (10,file='test.dat',form='unformatted',access='stream')
+  inquire (iolength=i) a
+  write (10) i, a, i
+  close (10)
+  open (10,file='test.dat',form='unformatted')
+  read (10) b
+  if (all (a == b)) print *,'success!'
+end program main
+</pre></div>
+
+<hr>
+<div class="header">
+<p>
+Next: <a href="Asynchronous-I_002fO.html#Asynchronous-I_002fO" accesskey="n" rel="next">Asynchronous I/O</a>, Previous: <a href="File-operations-on-symbolic-links.html#File-operations-on-symbolic-links" accesskey="p" rel="previous">File operations on symbolic links</a>, Up: <a href="Compiler-Characteristics.html#Compiler-Characteristics" accesskey="u" rel="up">Compiler Characteristics</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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