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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /><title>Hyperlinked ECMA C# Language Specification</title><meta name="author" content="Jon Jagger" /><link rel="stylesheet" href="ecma334.css"></link></head><body><div align="right"><em><a href="http://www.jaggersoft.com">Jon Jagger</a></em></div><div align="right"><a href="mailto:jon@jaggersoft.com">jon@jaggersoft.com</a></div><form method="get" action="http://search.atomz.com/search/"><input size="30" name="sp-q"></input><input type="submit" value="Search C# Spec"></input><input type="hidden" name="sp-a" value="sp10024177"></input><input type="hidden" name="sp-f" value="ISO-8859-1"></input></form><a href="toc.htm">Table of Contents</a> <a href="1.htm">1</a> <a href="2.htm">2</a> <a href="3.htm">3</a> <a href="4.htm">4</a> <a href="5.htm">5</a> <a href="6.htm">6</a> <a href="7.htm">7</a> <a href="8.htm">8</a> <a href="9.htm">9</a> <a href="10.htm">10</a> <a href="11.htm">11</a> <a href="12.htm">12</a> <a href="13.htm">13</a> <a href="14.htm">14</a> <a href="15.htm">15</a> <a href="16.htm">16</a> <a href="17.htm">17</a> <a href="18.htm">18</a> <a href="19.htm">19</a> <a href="20.htm">20</a> <a href="21.htm">21</a> <a href="22.htm">22</a> <a href="23.htm">23</a> <a href="24.htm">24</a> <a href="25.htm">25</a> <a href="notes.htm">Notes</a> <a href="HyperlinkedCSharpECMA.zip">Download</a><span class="ruler"></span><span class="heading">ECMA-334 C# Language Specification</span><span class="navigate"><a href="25.5.7.htm"><img src="previous.gif" alt="previous" border="0" /></a><a href="25.6.htm"><img src="next.gif" alt="next" border="0" /></a></span><span class="clause-depth"><a href="24.htm"><img src="previous.gif" alt="previous at this level" border="0" /></a><a href="25.htm"><img src="next.gif" alt="next at this level" border="0" /></a> <span class="clause-number-link"><a href="25.htm">25</a></span><span class="clause-title-previous"> Unsafe code</span></span><span class="clause-depth"><a href="25.4.htm"><img src="previous.gif" alt="previous at this level" border="0" /></a><a href="25.6.htm"><img src="next.gif" alt="next at this level" border="0" /></a> <span class="clause-number-link"><a href="25.5.htm">25.5</a></span><span class="clause-title-previous"> Pointers in expressions</span></span><span class="clause-depth"><a href="25.5.7.htm"><img src="previous.gif" alt="previous at this level" border="0" /></a><a href="25.5.8.htm"><img src="next.gif" alt="next at this level" border="0" /></a> <span class="clause-number">25.5.8</span><span class="clause-title"> The sizeof operator</span></span><span class="locator">
Paragraph 1</span><span class="paragraph"><span class="sentence"><span class="sentence-number">1</span> <a name="P1S1"></a>The sizeof operator returns the number of bytes occupied by a variable of a given type.</span> <span class="sentence"><span class="sentence-number">2</span> <a name="P1S2"></a>The type specified as an operand to sizeof must be an <span class="non-terminal"><a href="25.2.htm#unmanaged-type">unmanaged-type</a></span> (<a href="25.2.htm">§25.2</a>).</span> <span class="grammar-production"><span class="name"><a name="sizeof-expression"></a>sizeof-expression</span> : <span class="rhs"><span class="keyword">sizeof</span> <span class="terminal">(</span> <span class="non-terminal"><a href="25.2.htm#unmanaged-type">unmanaged-type</a></span> <span class="terminal">)</span> </span></span></span><span class="locator">
Paragraph 2</span><span class="paragraph"><span class="sentence"><span class="sentence-number">1</span> <a name="P2S1"></a>The result of the sizeof operator is a value of type <span class="keyword">int</span>.</span> <span class="sentence"><span class="sentence-number">2</span> <a name="P2S2"></a>For certain predefined types, the sizeof operator yields a constant value as shown in the table below.</span>
<table border="1">
<tr>
<th>Expression</th>
<th>Result</th>
</tr>
<tr>
<td>sizeof(sbyte)</td>
<td>1</td>
</tr>
<tr>
<td>sizeof(byte)</td>
<td>1</td>
</tr>
<tr>
<td>sizeof(short)</td>
<td>2</td>
</tr>
<tr>
<td>sizeof(ushort)</td>
<td>2</td>
</tr>
<tr>
<td>sizeof(int)</td>
<td>4</td>
</tr>
<tr>
<td>sizeof(uint)</td>
<td>4</td>
</tr>
<tr>
<td>sizeof(long)</td>
<td>8</td>
</tr>
<tr>
<td>sizeof(ulong)</td>
<td>8</td>
</tr>
<tr>
<td>sizeof(char)</td>
<td>2</td>
</tr>
<tr>
<td>sizeof(float)</td>
<td>4</td>
</tr>
<tr>
<td>sizeof(double)</td>
<td>8</td>
</tr>
<tr>
<td>sizeof(bool)</td>
<td>1</td>
</tr>
</table>
</span><span class="locator">
Paragraph 3</span><span class="paragraph"><span class="sentence"><span class="sentence-number">1</span> <a name="P3S1"></a>For all other types, the result of the sizeof operator is implementation-defined and is classified as a value, not a constant.</span> </span><span class="locator">
Paragraph 4</span><span class="paragraph"><span class="sentence"><span class="sentence-number">1</span> <a name="P4S1"></a>The order in which members are packed into a struct is unspecified.</span> </span><span class="locator">
Paragraph 5</span><span class="paragraph"><span class="sentence"><span class="sentence-number">1</span> <a name="P5S1"></a>For alignment purposes, there may be unnamed padding at the beginning of a struct, within a struct, and at the end of the struct.</span> <span class="sentence"><span class="sentence-number">2</span> <a name="P5S2"></a>The contents of the bits used as padding are indeterminate.</span> </span><span class="locator">
Paragraph 6</span><span class="paragraph"><span class="sentence"><span class="sentence-number">1</span> <a name="P6S1"></a>When applied to an operand that has struct type, the result is the total number of bytes in a variable of that type, including any padding.</span> </span><span class="ruler"></span><table><tr><td><table align="left" bgcolor="navy"><tr bgcolor="navy"><td><font face="Arial,sans-serif" size="6" color="yellow"><strong>{ JSL }</strong></font></td></tr></table></td></tr><tr><td><font face="Arial,sans-serif" size="2" color="navy"><strong>Jagger Software Ltd</strong></font></td></tr><tr><td><font face="Arial,sans-serif" size="2" color="navy"><strong>Company # 4070126</strong></font></td></tr><tr><td><font face="Arial,sans-serif" size="2" color="navy"><strong>VAT # 762 5213 42</strong></font></td></tr></table><img src="valid-html401.png" align="left" height="31" width="88" alt="Valid HTML 4.01" /><img src="vcss.gif" align="left" height="31" width="88" alt="Valid CSS" /></body></html>⌨️ 快捷键说明
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