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66Next: <a href="s390-Mnemonics.html#s390-Mnemonics" accesskey="n" rel="next">s390 Mnemonics</a>, Up: <a href="s390-Syntax.html#s390-Syntax" accesskey="u" rel="up">s390 Syntax</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="AS-Index.html#AS-Index" title="Index" rel="index">Index</a>]</p>
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69<a name="Register-naming"></a>
70<h4 class="subsubsection">9.41.3.1 Register naming</h4>
71<a name="index-register-naming_002c-s390"></a>
72<a name="index-s390-register-naming"></a>
73
74<p>The <code>as</code> recognizes a number of predefined symbols for the
75various processor registers. A register specification in one of the
76instruction formats is an unsigned integer between 0 and 15. The specific
77instruction and the position of the register in the instruction format
78denotes the type of the register. The register symbols are prefixed with
79&lsquo;<samp>%</samp>&rsquo;:
80</p>
81<div class="display">
82<table>
83<tr><td><pre class="display">%rN</pre></td><td><pre class="display">the 16 general purpose registers, 0 &lt;= N &lt;= 15</pre></td></tr>
84<tr><td><pre class="display">%fN</pre></td><td><pre class="display">the 16 floating point registers, 0 &lt;= N &lt;= 15</pre></td></tr>
85<tr><td><pre class="display">%aN</pre></td><td><pre class="display">the 16 access registers, 0 &lt;= N &lt;= 15</pre></td></tr>
86<tr><td><pre class="display">%cN</pre></td><td><pre class="display">the 16 control registers, 0 &lt;= N &lt;= 15</pre></td></tr>
87<tr><td><pre class="display">%lit</pre></td><td><pre class="display">an alias for the general purpose register %r13</pre></td></tr>
88<tr><td><pre class="display">%sp</pre></td><td><pre class="display">an alias for the general purpose register %r15</pre></td></tr>
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