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<p ALIGN="JUSTIFY" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2" color="#008000"><font FACE="??ì?,SimSun" LANG="ZH-CN">循环体</font>;</font></p>
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<p ALIGN="JUSTIFY" style="line-height: 100%; margin-top: 0; margin-bottom: 0"></font><font FACE="??ì?,SimSun" LANG="ZH-CN" size="2">执行过程如下：</font></p>
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<p ALIGN="JUSTIFY" style="line-height: 100%; margin-top: 0; margin-bottom: 0"></font><font size="2"><font FACE="??ì?,SimSun" LANG="ZH-CN">①
先求解表达式</font>1<font FACE="??ì?,SimSun" LANG="ZH-CN">，表达式</font>1<font FACE="??ì?,SimSun" LANG="ZH-CN">只执行一次，</font></font></p>
<p ALIGN="JUSTIFY" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font FACE="??ì?,SimSun" LANG="ZH-CN" size="2">一般是赋值语句，用于初始化变量。</font></p>
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<p ALIGN="JUSTIFY" style="line-height: 100%; margin-top: 0; margin-bottom: 0"></font><font size="2"><font FACE="??ì?,SimSun" LANG="ZH-CN">②</font>
<font FACE="??ì?,SimSun" LANG="ZH-CN">求解表达式</font>2<font FACE="??ì?,SimSun" LANG="ZH-CN">，若为假（</font>0<font FACE="??ì?,SimSun" LANG="ZH-CN">），则结束循环。</font></font></p>
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<p ALIGN="JUSTIFY" style="line-height: 100%; margin-top: 0; margin-bottom: 0"></font><font size="2"><font FACE="??ì?,SimSun" LANG="ZH-CN">③</font>
<font FACE="??ì?,SimSun" LANG="ZH-CN">执行循环体。</font></font></p>
<p ALIGN="JUSTIFY" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2"><font FACE="??ì?,SimSun" LANG="ZH-CN">④</font>
<font FACE="??ì?,SimSun" LANG="ZH-CN">执行表达式</font>3<font FACE="??ì?,SimSun" LANG="ZH-CN">。</font></font></p>
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<p style="line-height: 100%; margin-top: 0; margin-bottom: 0"></font><font size="2"><font FACE="??ì?,SimSun" LANG="ZH-CN">⑤</font>
<font FACE="??ì?,SimSun" LANG="ZH-CN">转回②。</font></font></p>
<p style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2"><font FACE="??ì?,SimSun" LANG="ZH-CN"><a href="example2-8.htm" target="_blank">【例</a></font><a href="example2-8.htm" target="_blank">2-8<font FACE="??ì?,SimSun" LANG="ZH-CN">】</font></a><font FACE="??ì?,SimSun" LANG="ZH-CN">求</font>1+2+3+<font FACE="??ì?,SimSun" LANG="ZH-CN">…</font>+100<font FACE="??ì?,SimSun" LANG="ZH-CN">的值。</font></font></p>
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<p ALIGN="JUSTIFY" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2"><font FACE="??ì?,SimSun" LANG="ZH-CN">说明：表达式</font>1<font FACE="??ì?,SimSun" LANG="ZH-CN">，表达式</font>2<font FACE="??ì?,SimSun" LANG="ZH-CN">，表达式</font>3<font FACE="??ì?,SimSun" LANG="ZH-CN">和循环体可以省略，例如上述</font>for<font FACE="??ì?,SimSun" LANG="ZH-CN">语句可以改为：</font></font></p>
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<p ALIGN="JUSTIFY" style="line-height: 100%; margin-top: 0; margin-bottom: 0"></font><font size="2"><font FACE="??ì?,SimSun" LANG="ZH-CN">①
</font>int i=1,sum=0; //<font FACE="??ì?,SimSun" LANG="ZH-CN">表达式</font>1<font FACE="??ì?,SimSun" LANG="ZH-CN">放在</font>for<font FACE="??ì?,SimSun" LANG="ZH-CN">前面。</font></font></p>
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for(;i<=100;i++)</font></p>
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sum+=i;</font></p>
<p ALIGN="JUSTIFY" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2"><font FACE="??ì?,SimSun" LANG="ZH-CN">②</font>
int i=1,sum=0;</font></p>
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for(;i<=100;)</font></p>
<p ALIGN="JUSTIFY" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">
sum+=i++; //<font FACE="??ì?,SimSun" LANG="ZH-CN">表达式</font>3<font FACE="??ì?,SimSun" LANG="ZH-CN">放在</font>for<font FACE="??ì?,SimSun" LANG="ZH-CN">循环体中。</font></font></p>
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<p ALIGN="JUSTIFY" style="line-height: 100%; margin-top: 0; margin-bottom: 0"></font><font size="2"><font FACE="??ì?,SimSun" LANG="ZH-CN">③</font>
int i=1,sum=0;</font></p>
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for ( ; ; )</font></p>
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{</font></p>
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sum+=i++;</font></p>
<p ALIGN="JUSTIFY" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">
if(i>100) //<font FACE="??ì?,SimSun" LANG="ZH-CN">强制结束循环</font></font></p>
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break;</font></p>
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}</font></p>
<p ALIGN="JUSTIFY" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2"><font FACE="??ì?,SimSun" LANG="ZH-CN">④</font>
for (int i=1,sum=0; i<=100;sum+=i++); //<font FACE="??ì?,SimSun" LANG="ZH-CN">省略循环体</font></font></p>
<p ALIGN="JUSTIFY" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2"><font FACE="??ì?,SimSun" LANG="ZH-CN">⑤</font>
for (int i=1,sum=0; sum+=i++, i<=100;); //<font FACE="??ì?,SimSun" LANG="ZH-CN">省略表达式</font>3<font FACE="??ì?,SimSun" LANG="ZH-CN">和循环体。</font></font></p>
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<p ALIGN="JUSTIFY" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">7.
</font><font FACE="??ì?,SimSun" LANG="ZH-CN"><font size="2">转向控制语句</font></p>
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<p style="line-height: 100%; margin-top: 0; margin-bottom: 0"></font><font size="2"><font FACE="??ì?,SimSun" LANG="ZH-CN">转向语句有三个，分别是：</font>break<font FACE="??ì?,SimSun" LANG="ZH-CN">，</font>continue<font FACE="??ì?,SimSun" LANG="ZH-CN">和</font>goto<font FACE="??ì?,SimSun" LANG="ZH-CN">语句。</font></font></p>
<p ALIGN="JUSTIFY" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font FACE="oúì?,SimHei" LANG="ZH-CN" size="2"><i>1.
break语句</i></font></p>
<p style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">break<font FACE="??ì?,SimSun" LANG="ZH-CN">语句可以用在循环语句和</font>switch<font FACE="??ì?,SimSun" LANG="ZH-CN">语句中。在循环语句中用来结束内部循环；在</font>switch<font FACE="??ì?,SimSun" LANG="ZH-CN">语句中用来跳出</font>switch<font FACE="??ì?,SimSun" LANG="ZH-CN">语句。</font></font></p>
<p style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2"><font FACE="??ì?,SimSun" LANG="ZH-CN"><a href="example2-9.htm" target="_blank">【例</a></font><a href="example2-9.htm" target="_blank">2-9<font FACE="??ì?,SimSun" LANG="ZH-CN">】</font></a>break<font FACE="??ì?,SimSun" LANG="ZH-CN">用在循环语句中。</font></font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 5; margin-bottom: 0"><font FACE="oúì?,SimHei" LANG="ZH-CN" size="2"><i>2.
continue语句</i></font></p>
<p ALIGN="JUSTIFY" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">continue<font FACE="??ì?,SimSun" LANG="ZH-CN">语句的作用是结束本次循环，忽略</font>continue<font FACE="??ì?,SimSun" LANG="ZH-CN">后面的语句，进行下一次循环判定。</font></font></p>
<p ALIGN="JUSTIFY" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2"><font FACE="??ì?,SimSun" LANG="ZH-CN"><a href="example2-10.htm">【例</a></font><a href="example2-10.htm">2-10<font FACE="??ì?,SimSun" LANG="ZH-CN">】</font></a><font FACE="??ì?,SimSun" LANG="ZH-CN">编程从键盘上输入</font>10<font FACE="??ì?,SimSun" LANG="ZH-CN">个数，计算所有正数之和。</font></font></p>
<p style="line-height: 100%; margin-top: 5; margin-bottom: 0"><font size="2"><i>3.
goto<font FACE="??ì?,SimSun" LANG="ZH-CN">语句</font></i></font></p>
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