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| <h5 class="subsubsection">3.6.1.1 Strings</h5> |
| |
| <p><a name="index-string-constants-144"></a><a name="index-constants_002c-string-145"></a>A <dfn>string</dfn> is written between double-quotes. It may contain |
| double-quotes or null characters. The way to get special characters |
| into a string is to <dfn>escape</dfn> these characters: precede them with |
| a backslash ‘<samp><span class="samp">\</span></samp>’ character. For example ‘<samp><span class="samp">\\</span></samp>’ represents |
| one backslash: the first <code>\</code> is an escape which tells |
| <samp><span class="command">as</span></samp> to interpret the second character literally as a backslash |
| (which prevents <samp><span class="command">as</span></samp> from recognizing the second <code>\</code> as an |
| escape character). The complete list of escapes follows. |
| |
| <p><a name="index-escape-codes_002c-character-146"></a><a name="index-character-escape-codes-147"></a><!-- NOTE: Cindex entries must not start with a backlash character. --> |
| <!-- NOTE: This confuses the pdf2texi script when it is creating the --> |
| <!-- NOTE: index based upon the first character and so it generates: --> |
| <!-- NOTE: \initial {\\} --> |
| <!-- NOTE: which then results in the error message: --> |
| <!-- NOTE: Argument of \\ has an extra }. --> |
| <!-- NOTE: So in the index entries below a space character has been --> |
| <!-- NOTE: prepended to avoid this problem. --> |
| <dl> |
| <!-- @item \a --> |
| <!-- Mnemonic for ACKnowledge; for ASCII this is octal code 007. --> |
| <a name="index-g_t_0040code_007b-_005cb_007d-_0028backspace-character_0029-148"></a><a name="index-backspace-_0028_0040code_007b_005cb_007d_0029-149"></a><dt><kbd>\b</kbd><dd>Mnemonic for backspace; for ASCII this is octal code 010. |
| |
| <!-- @item \e --> |
| <!-- Mnemonic for EOText; for ASCII this is octal code 004. --> |
| <p><a name="index-g_t_0040code_007b-_005cf_007d-_0028formfeed-character_0029-150"></a><a name="index-formfeed-_0028_0040code_007b_005cf_007d_0029-151"></a><br><dt><kbd>backslash-f</kbd><dd>Mnemonic for FormFeed; for ASCII this is octal code 014. |
| |
| <p><a name="index-g_t_0040code_007b-_005cn_007d-_0028newline-character_0029-152"></a><a name="index-newline-_0028_0040code_007b_005cn_007d_0029-153"></a><br><dt><kbd>\n</kbd><dd>Mnemonic for newline; for ASCII this is octal code 012. |
| |
| <!-- @item \p --> |
| <!-- Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}. --> |
| <p><a name="index-g_t_0040code_007b-_005cr_007d-_0028carriage-return-character_0029-154"></a><a name="index-carriage-return-_0028_0040code_007bbackslash_002dr_007d_0029-155"></a><br><dt><kbd>\r</kbd><dd>Mnemonic for carriage-Return; for ASCII this is octal code 015. |
| |
| <!-- @item \s --> |
| <!-- Mnemonic for space; for ASCII this is octal code 040. Included for compliance with --> |
| <!-- other assemblers. --> |
| <p><a name="index-g_t_0040code_007b-_005ct_007d-_0028tab_0029-156"></a><a name="index-tab-_0028_0040code_007b_005ct_007d_0029-157"></a><br><dt><kbd>\t</kbd><dd>Mnemonic for horizontal Tab; for ASCII this is octal code 011. |
| |
| <!-- @item \v --> |
| <!-- Mnemonic for Vertical tab; for ASCII this is octal code 013. --> |
| <!-- @item \x @var{digit} @var{digit} @var{digit} --> |
| <!-- A hexadecimal character code. The numeric code is 3 hexadecimal digits. --> |
| <p><a name="index-g_t_0040code_007b-_005c_0040var_007bddd_007d_007d-_0028octal-character-code_0029-158"></a><a name="index-octal-character-code-_0028_0040code_007b_005c_0040var_007bddd_007d_007d_0029-159"></a><br><dt><kbd>\ </kbd><var>digit</var> <var>digit</var> <var>digit</var><dd>An octal character code. The numeric code is 3 octal digits. |
| For compatibility with other Unix systems, 8 and 9 are accepted as digits: |
| for example, <code>\008</code> has the value 010, and <code>\009</code> the value 011. |
| |
| <p><a name="index-g_t_0040code_007b-_005c_0040var_007bxd_002e_002e_002e_007d_007d-_0028hex-character-code_0029-160"></a><a name="index-hex-character-code-_0028_0040code_007b_005c_0040var_007bxd_002e_002e_002e_007d_007d_0029-161"></a><br><dt><kbd>\</kbd><code>x</code> <var>hex-digits...</var><dd>A hex character code. All trailing hex digits are combined. Either upper or |
| lower case <code>x</code> works. |
| |
| <p><a name="index-g_t_0040code_007b-_005c_005c_007d-_0028_0040samp_007b_005c_007d-character_0029-162"></a><a name="index-backslash-_0028_0040code_007b_005c_005c_007d_0029-163"></a><br><dt><kbd>\\</kbd><dd>Represents one ‘<samp><span class="samp">\</span></samp>’ character. |
| |
| <!-- @item \' --> |
| <!-- Represents one @samp{'} (accent acute) character. --> |
| <!-- This is needed in single character literals --> |
| <!-- (@xref{Characters,,Character Constants}.) to represent --> |
| <!-- a @samp{'}. --> |
| <p><a name="index-g_t_0040code_007b-_005c_0022_007d-_0028doublequote-character_0029-164"></a><a name="index-doublequote-_0028_0040code_007b_005c_0022_007d_0029-165"></a><br><dt><kbd>\"</kbd><dd>Represents one ‘<samp><span class="samp">"</span></samp>’ character. Needed in strings to represent |
| this character, because an unescaped ‘<samp><span class="samp">"</span></samp>’ would end the string. |
| |
| <br><dt><kbd>\ </kbd><var>anything-else</var><dd>Any other character when escaped by <kbd>\</kbd> gives a warning, but |
| assembles as if the ‘<samp><span class="samp">\</span></samp>’ was not present. The idea is that if |
| you used an escape sequence you clearly didn't want the literal |
| interpretation of the following character. However <samp><span class="command">as</span></samp> has no |
| other interpretation, so <samp><span class="command">as</span></samp> knows it is giving you the wrong |
| code and warns you of the fact. |
| </dl> |
| |
| <p>Which characters are escapable, and what those escapes represent, |
| varies widely among assemblers. The current set is what we think |
| the BSD 4.2 assembler recognizes, and is a subset of what most C |
| compilers recognize. If you are in doubt, do not use an escape |
| sequence. |
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