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  1. <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

  2. <html>

  3. <!-- This file documents the GNU Assembler "as".

  4. 

  5. Copyright (C) 1991-2020 Free Software Foundation, Inc.

  6. 

  7. Permission is granted to copy, distribute and/or modify this document

  8. under the terms of the GNU Free Documentation License, Version 1.3

  9. or any later version published by the Free Software Foundation;

  10. with no Invariant Sections, with no Front-Cover Texts, and with no

  11. Back-Cover Texts.  A copy of the license is included in the

  12. section entitled "GNU Free Documentation License".

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  15. <head>

  16. <meta http-equiv="Content-Type" content="text/html; charset=utf-8">

  17. <title>MMIX-Symbols (Using as)</title>

  18. 

  19. <meta name="description" content="MMIX-Symbols (Using as)">

  20. <meta name="keywords" content="MMIX-Symbols (Using as)">

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  25. <link href="AS-Index.html#AS-Index" rel="index" title="AS Index">

  26. <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">

  27. <link href="MMIX_002dSyntax.html#MMIX_002dSyntax" rel="up" title="MMIX-Syntax">

  28. <link href="MMIX_002dRegs.html#MMIX_002dRegs" rel="next" title="MMIX-Regs">

  29. <link href="MMIX_002dChars.html#MMIX_002dChars" rel="prev" title="MMIX-Chars">

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  57. 

  58. 

  59. </head>

  60. 

  61. <body lang="en">

  62. <a name="MMIX_002dSymbols"></a>

  63. <div class="header">

  64. <p>

  65. Next: <a href="MMIX_002dRegs.html#MMIX_002dRegs" accesskey="n" rel="next">MMIX-Regs</a>, Previous: <a href="MMIX_002dChars.html#MMIX_002dChars" accesskey="p" rel="prev">MMIX-Chars</a>, Up: <a href="MMIX_002dSyntax.html#MMIX_002dSyntax" accesskey="u" rel="up">MMIX-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>

  66. </div>

  67. <hr>

  68. <a name="Symbols-4"></a>

  69. <h4 class="subsubsection">9.28.3.2 Symbols</h4>

  70. <p>The character &lsquo;<samp>:</samp>&rsquo; is permitted in identifiers.  There are two

  71. exceptions to it being treated as any other symbol character: if a symbol

  72. begins with &lsquo;<samp>:</samp>&rsquo;, it means that the symbol is in the global namespace

  73. and that the current prefix should not be prepended to that symbol

  74. (see <a href="MMIX_002dPseudos.html#MMIX_002dprefix">MMIX-prefix</a>).  The &lsquo;<samp>:</samp>&rsquo; is then not considered part of the

  75. symbol.  For a symbol in the label position (first on a line), a &lsquo;<samp>:</samp>&rsquo;

  76. at the end of a symbol is silently stripped off.  A label is permitted,

  77. but not required, to be followed by a &lsquo;<samp>:</samp>&rsquo;, as with many other

  78. assembly formats.

  79. </p>

  80. <p>The character &lsquo;<samp>@</samp>&rsquo; in an expression, is a synonym for &lsquo;<samp>.</samp>&rsquo;, the

  81. current location.

  82. </p>

  83. <p>In addition to the common forward and backward local symbol formats

  84. (see <a href="Symbol-Names.html#Symbol-Names">Symbol Names</a>), they can be specified with upper-case &lsquo;<samp>B</samp>&rsquo; and

  85. &lsquo;<samp>F</samp>&rsquo;, as in &lsquo;<samp>8B</samp>&rsquo; and &lsquo;<samp>9F</samp>&rsquo;.  A local label defined for the

  86. current position is written with a &lsquo;<samp>H</samp>&rsquo; appended to the number:

  87. </p><div class="smallexample">

  88. <pre class="smallexample">3H LDB $0,$1,2

  89. </pre></div>

  90. <p>This and traditional local-label formats cannot be mixed: a label must be

  91. defined and referred to using the same format.

  92. </p>

  93. <p>There&rsquo;s a minor caveat: just as for the ordinary local symbols, the local

  94. symbols are translated into ordinary symbols using control characters are

  95. to hide the ordinal number of the symbol.  Unfortunately, these symbols

  96. are not translated back in error messages.  Thus you may see confusing

  97. error messages when local symbols are used.  Control characters

  98. &lsquo;<samp>\003</samp>&rsquo; (control-C) and &lsquo;<samp>\004</samp>&rsquo; (control-D) are used for the

  99. MMIX-specific local-symbol syntax.

  100. </p>

  101. <p>The symbol &lsquo;<samp>Main</samp>&rsquo; is handled specially; it is always global.

  102. </p>

  103. <p>By defining the symbols &lsquo;<samp>__.MMIX.start..text</samp>&rsquo; and

  104. &lsquo;<samp>__.MMIX.start..data</samp>&rsquo;, the address of respectively the &lsquo;<samp>.text</samp>&rsquo;

  105. and &lsquo;<samp>.data</samp>&rsquo; segments of the final program can be defined, though when

  106. linking more than one object file, the code or data in the object file

  107. containing the symbol is not guaranteed to be start at that position; just

  108. the final executable.  See <a href="MMIX_002dPseudos.html#MMIX_002dloc">MMIX-loc</a>.

  109. </p>

  110. <hr>

  111. <div class="header">

  112. <p>

  113. Next: <a href="MMIX_002dRegs.html#MMIX_002dRegs" accesskey="n" rel="next">MMIX-Regs</a>, Previous: <a href="MMIX_002dChars.html#MMIX_002dChars" accesskey="p" rel="prev">MMIX-Chars</a>, Up: <a href="MMIX_002dSyntax.html#MMIX_002dSyntax" accesskey="u" rel="up">MMIX-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>

  114. </div>

  115. 

  116. 

  117. 

  118. </body>

  119. </html>