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90 lines
4.6 KiB
HTML
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<title>Statements - Using as</title>
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<link rel="up" href="Syntax.html#Syntax" title="Syntax">
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<!--
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This file documents the GNU Assembler "as".
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Copyright (C) 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001, 2002,
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2006, 2007 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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<p>
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<a name="Statements"></a>Next: <a rel="next" accesskey="n" href="Constants.html#Constants">Constants</a>,
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Previous: <a rel="previous" accesskey="p" href="Symbol-Intro.html#Symbol-Intro">Symbol Intro</a>,
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Up: <a rel="up" accesskey="u" href="Syntax.html#Syntax">Syntax</a>
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<hr><br>
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</div>
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<h3 class="section">3.5 Statements</h3>
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<p><a name="index-statements_002c-structure-of-130"></a><a name="index-line-separator-character-131"></a><a name="index-statement-separator-character-132"></a>A <dfn>statement</dfn> ends at a newline character (<span class="samp">\n</span>) or line
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separator character. (The line separator is usually <span class="samp">;</span>, unless this
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conflicts with the comment character; see <a href="Machine-Dependencies.html#Machine-Dependencies">Machine Dependencies</a>.) The
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newline or separator character is considered part of the preceding
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statement. Newlines and separators within character constants are an
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exception: they do not end statements.
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<p><a name="index-newline_002c-required-at-file-end-133"></a><a name="index-EOF_002c-newline-must-precede-134"></a>It is an error to end any statement with end-of-file: the last
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character of any input file should be a newline.
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<p>An empty statement is allowed, and may include whitespace. It is ignored.
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<p><a name="index-instructions-and-directives-135"></a><a name="index-directives-and-instructions-136"></a><!-- "key symbol" is not used elsewhere in the document; seems pedantic to -->
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<!-- @defn{} it in that case, as was done previously... doc@cygnus.com, -->
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<!-- 13feb91. -->
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A statement begins with zero or more labels, optionally followed by a
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key symbol which determines what kind of statement it is. The key
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symbol determines the syntax of the rest of the statement. If the
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symbol begins with a dot <span class="samp">.</span> then the statement is an assembler
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directive: typically valid for any computer. If the symbol begins with
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a letter the statement is an assembly language <dfn>instruction</dfn>: it
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assembles into a machine language instruction.
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Different versions of <span class="command">as</span> for different computers
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recognize different instructions. In fact, the same symbol may
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represent a different instruction in a different computer's assembly
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language.
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<p><a name="index-_0040code_007b_003a_007d-_0028label_0029-137"></a><a name="index-label-_0028_0040code_007b_003a_007d_0029-138"></a>A label is a symbol immediately followed by a colon (<code>:</code>).
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Whitespace before a label or after a colon is permitted, but you may not
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have whitespace between a label's symbol and its colon. See <a href="Labels.html#Labels">Labels</a>.
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<p>For HPPA targets, labels need not be immediately followed by a colon, but
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the definition of a label must begin in column zero. This also implies that
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only one label may be defined on each line.
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<pre class="smallexample"> label: .directive followed by something
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another_label: # This is an empty statement.
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instruction operand_1, operand_2, ...
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</pre>
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</body></html>
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