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📁 Fortran77和90/95编程入门,用于教学
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<body bgcolor="#DDFFEE" lang=ZH-TW link=blue vlink=purple style='tab-interval:
21.0pt;text-justify-trim:punctuation'>

<div class=Section1 style='layout-grid:15.6pt'>

<p align=center style='margin:0cm;margin-bottom:.0001pt;text-align:center'><b
style='mso-bidi-font-weight:normal'><span lang=ZH-CN style='font-size:22.0pt;
font-family:楷体_GB2312;mso-hansi-font-family:宋体;color:black'>第三章</span></b><b
style='mso-bidi-font-weight:normal'><span lang=EN-US style='font-size:22.0pt;
font-family:楷体_GB2312;mso-hansi-font-family:宋体;color:black'>: </span></b><b
style='mso-bidi-font-weight:normal'><span lang=ZH-CN style='font-size:22.0pt;
font-family:楷体_GB2312;mso-hansi-font-family:宋体;color:black'>循环结构</span></b><b
style='mso-bidi-font-weight:normal'><span lang=EN-US style='font-size:22.0pt;
font-family:楷体_GB2312;mso-hansi-font-family:宋体;color:black'><o:p></o:p></span></b></p>

<p class=MsoNormal align=center style='margin-top:15.6pt;margin-right:0cm;
margin-bottom:15.6pt;margin-left:0cm;mso-para-margin-top:1.0gd;mso-para-margin-right:
0cm;mso-para-margin-bottom:1.0gd;mso-para-margin-left:0cm;text-align:center'><b><span
lang=ZH-CN style='font-size:22.0pt;font-family:华文细黑;color:#333399'>单纯循环</span></b><b><span
lang=EN-US style='font-size:22.0pt;font-family:华文细黑;color:#333399'><o:p></o:p></span></b></p>

<p class=MsoNormal align=center style='margin-top:15.6pt;margin-right:0cm;
margin-bottom:15.6pt;margin-left:0cm;mso-para-margin-top:1.0gd;mso-para-margin-right:
0cm;mso-para-margin-bottom:1.0gd;mso-para-margin-left:0cm;text-align:center'><a
name="第3_1_1"><span lang=EN-US style='font-size:16.0pt;mso-bidi-font-size:12.0pt;
mso-fareast-font-family:楷体_GB2312'>3.1.1</span></a><span lang=EN-US
style='font-size:16.0pt;mso-bidi-font-size:12.0pt;mso-fareast-font-family:楷体_GB2312'>
<span style='color:red'>GOTO</span></span><span lang=ZH-CN style='font-size:
16.0pt;mso-bidi-font-size:12.0pt;font-family:楷体_GB2312;mso-ascii-font-family:
"Times New Roman";color:red'>语句实现循环</span><b><span lang=EN-US style='font-size:
16.0pt;mso-bidi-font-size:12.0pt;mso-fareast-font-family:楷体_GB2312'><o:p></o:p></span></b></p>

<p class=MsoBodyTextIndent2 style='line-height:17.0pt;mso-line-height-rule:
exactly;mso-char-indent-size:12pt'><span lang=ZH-CN>循环结构用于实现重复的算法。它是三种基本结构（顺序、选择、循环）之一，具有重复执行某一段语句的功能，因为它以</span><span
lang=EN-US>DO</span><span lang=ZH-CN>作为关键字，所以又称</span><span lang=EN-US>DO</span><span
lang=ZH-CN>构造。在程序中存在两类循环：无条件的循环和有条件的循环。无条件循环是无休止地执行一个程序段，而有条件的循环是在满足一定条件时才执行循环。</span></p>

<p class=MsoBodyTextIndent2 style='line-height:17.0pt;mso-line-height-rule:
exactly'><span lang=EN-US>F77</span><span lang=ZH-CN>允许使用</span><span
lang=EN-US>GOTO</span><span lang=ZH-CN>语句来实现转移。</span><span lang=EN-US>GOTO</span><span
lang=ZH-CN>语句的一般形式为：</span><span lang=EN-US style='color:#FF6600;mso-font-kerning:
0pt'>GOTO (</span><span lang=ZH-CN style='color:#FF6600;mso-font-kerning:0pt'>语句标号</span><span
lang=EN-US style='color:#FF6600;mso-font-kerning:0pt'>)</span><span lang=ZH-CN>。由于</span><span
lang=EN-US>GOTO</span><span lang=ZH-CN>语句破坏了语句顺序执行的正常状况，不符合结构化原则，因此一般不提倡使用</span><span
lang=EN-US>GOTO</span><span lang=ZH-CN>语句。只有在一个基本结构内部可以使用</span><span
lang=EN-US>GOTO</span><span lang=ZH-CN>语句。利用</span><span lang=EN-US>GOTO</span><span
lang=ZH-CN>语句可以实现循环处理。如果在逻辑</span><span lang=EN-US>IF</span><span lang=ZH-CN>语句中使用</span><span
lang=EN-US>GOTO</span><span lang=ZH-CN>语句就可以实现有条件的循环，循环操作能够在一定条件下结束。</span></p>

<p class=MsoNormal align=center style='margin-top:15.6pt;margin-right:0cm;
margin-bottom:15.6pt;margin-left:0cm;mso-para-margin-top:1.0gd;mso-para-margin-right:
0cm;mso-para-margin-bottom:1.0gd;mso-para-margin-left:0cm;text-align:center'><a
name="第3_1_2"><span lang=EN-US style='font-size:16.0pt;mso-bidi-font-size:12.0pt;
mso-fareast-font-family:楷体_GB2312'>3.1.2</span></a><span style='mso-bookmark:
第3_1_2'></span><span lang=ZH-CN style='font-size:16.0pt;mso-bidi-font-size:
12.0pt;font-family:楷体_GB2312;mso-ascii-font-family:"Times New Roman";
color:red'>有循环变量的</span><span lang=EN-US style='font-size:16.0pt;mso-bidi-font-size:
12.0pt;mso-fareast-font-family:楷体_GB2312;color:red'>DO</span><span lang=ZH-CN
style='font-size:16.0pt;mso-bidi-font-size:12.0pt;font-family:楷体_GB2312;
mso-ascii-font-family:"Times New Roman";color:red'>构造</span><b><span
lang=EN-US style='font-size:16.0pt;mso-bidi-font-size:12.0pt;mso-fareast-font-family:
楷体_GB2312'><o:p></o:p></span></b></p>

<p style='margin-left:18.0pt;text-indent:-18.0pt;mso-list:l10 level1 lfo2;
tab-stops:list 18.0pt;mso-char-indent-size:12pt'><a name="第3_1_2a"></a><![if !supportLists]><span
lang=EN-US style='font-family:宋体;mso-bidi-font-family:宋体;color:red'><span
style='mso-list:Ignore'>a)<span style='font:7.0pt "Times New Roman"'>&nbsp;&nbsp;&nbsp;
</span></span></span><![endif]><span lang=EN-US style='font-family:宋体;
color:red'>DO</span><span lang=ZH-CN style='font-family:宋体;color:red'>语句和循环次数</span><span
lang=EN-US style='font-family:宋体;color:red'><o:p></o:p></span></p>

<p class=MsoBodyTextIndent2 style='line-height:17.0pt;mso-line-height-rule:
exactly'><span lang=EN-US>DO</span><span lang=ZH-CN>构造可分为不带循环变量与带循环变量两种形式。</span><span
lang=EN-US style='mso-font-kerning:0pt'><o:p></o:p></span></p>

<p class=MsoBodyTextIndent2 style='line-height:17.0pt;mso-line-height-rule:
exactly'><span lang=ZH-CN style='mso-font-kerning:0pt'>当需要执行的循环次数为已知时，用</span><span
lang=EN-US style='mso-font-kerning:0pt'>DO</span><span lang=ZH-CN
style='mso-font-kerning:0pt'>语句实现循环比较方便。它的一般形式为：</span><span lang=EN-US
style='mso-font-kerning:0pt'><o:p></o:p></span></p>

<p class=MsoBodyTextIndent2 style='line-height:17.0pt;mso-line-height-rule:
exactly'><span lang=EN-US style='color:#FF6600;mso-font-kerning:0pt'>DO [[</span><span
lang=ZH-CN style='color:#FF6600;mso-font-kerning:0pt'>标号</span><span
lang=EN-US style='color:#FF6600;mso-font-kerning:0pt'>][</span><span
lang=ZH-CN style='color:#FF6600;mso-font-kerning:0pt'>，</span><span lang=EN-US
style='color:#FF6600;mso-font-kerning:0pt'>]] </span><span lang=ZH-CN
style='color:#FF6600;mso-font-kerning:0pt'>循环变量＝初值式，终值式</span><span lang=EN-US
style='color:#FF6600;mso-font-kerning:0pt'>[</span><span lang=ZH-CN
style='color:#FF6600;mso-font-kerning:0pt'>，增量式</span><span lang=EN-US
style='color:#FF6600;mso-font-kerning:0pt'>]<o:p></o:p></span></p>

<p class=MsoBodyTextIndent2 style='line-height:17.0pt;mso-line-height-rule:
exactly'><span lang=ZH-CN style='mso-font-kerning:0pt'>例：循环读入学生的学号和成绩</span><span
lang=EN-US style='mso-font-kerning:0pt'>30</span><span lang=ZH-CN
style='mso-font-kerning:0pt'>次并打印。</span><span lang=EN-US style='mso-font-kerning:
0pt'><o:p></o:p></span></p>

<p class=MsoBodyTextIndent2 style='margin-left:42.5pt;mso-para-margin-left:
4.05gd;text-indent:48.0pt;mso-char-indent-count:4.0;line-height:15.0pt;
mso-line-height-rule:exactly;mso-char-indent-size:12pt'><span lang=EN-US
style='mso-font-kerning:0pt'>DO 10, N</span><span lang=ZH-CN style='mso-font-kerning:
0pt'>＝</span><span lang=EN-US style='mso-font-kerning:0pt'>1</span><span
lang=ZH-CN style='mso-font-kerning:0pt'>，</span><span lang=EN-US
style='mso-font-kerning:0pt'>30</span><span lang=ZH-CN style='mso-font-kerning:
0pt'>，</span><span lang=EN-US style='mso-font-kerning:0pt'>1<o:p></o:p></span></p>

<p class=MsoBodyTextIndent2 style='margin-left:42.5pt;mso-para-margin-left:
4.05gd;text-indent:72.0pt;mso-char-indent-count:6.0;line-height:15.0pt;
mso-line-height-rule:exactly;mso-char-indent-size:12pt'><span lang=EN-US
style='mso-font-kerning:0pt'>READ *</span><span lang=ZH-CN style='mso-font-kerning:
0pt'>，</span><span lang=EN-US style='mso-font-kerning:0pt'>NUM</span><span
lang=ZH-CN style='mso-font-kerning:0pt'>，</span><span lang=EN-US
style='mso-font-kerning:0pt'>GRADE<o:p></o:p></span></p>

<p class=MsoBodyTextIndent2 style='margin-left:42.5pt;mso-para-margin-left:
4.05gd;line-height:15.0pt;mso-line-height-rule:exactly'><span lang=EN-US
style='mso-font-kerning:0pt'>10<span style='mso-spacerun:yes'>&nbsp;
</span>PRINT *</span><span lang=ZH-CN style='mso-font-kerning:0pt'>，</span><span
lang=EN-US style='mso-font-kerning:0pt'>NUM</span><span lang=ZH-CN
style='mso-font-kerning:0pt'>，</span><span lang=EN-US style='mso-font-kerning:
0pt'>GRADE<o:p></o:p></span></p>

<p class=MsoBodyTextIndent2 style='line-height:17.0pt;mso-line-height-rule:
exactly'><span lang=ZH-CN style='mso-font-kerning:0pt'>上面是一个循环，第一行</span><span
lang=EN-US style='mso-font-kerning:0pt'>DO</span><span lang=ZH-CN
style='mso-font-kerning:0pt'>语句称为循环语句，</span><span lang=EN-US style='mso-font-kerning:
0pt'>DO</span><span lang=ZH-CN style='mso-font-kerning:0pt'>后面的数</span><span
lang=EN-US style='mso-font-kerning:0pt'>10</span><span lang=ZH-CN
style='mso-font-kerning:0pt'>是一个标号，表示循环的范围到标号为</span><span lang=EN-US
style='mso-font-kerning:0pt'>10</span><span lang=ZH-CN style='mso-font-kerning:
0pt'>的语句为止，也就是反复执行</span><span lang=EN-US style='mso-font-kerning:0pt'>READ</span><span
lang=ZH-CN style='mso-font-kerning:0pt'>语句和</span><span lang=EN-US
style='mso-font-kerning:0pt'>PRINT</span><span lang=ZH-CN style='mso-font-kerning:
0pt'>语句。</span><span lang=EN-US style='mso-font-kerning:0pt'>DO</span><span
lang=ZH-CN style='mso-font-kerning:0pt'>语句中的</span><span lang=EN-US
style='mso-font-kerning:0pt'>N</span><span lang=ZH-CN style='mso-font-kerning:
0pt'>是“循环变量”，用它来控制循环次数，“</span><span lang=EN-US style='mso-font-kerning:0pt'>N</span><span
lang=ZH-CN style='mso-font-kerning:0pt'>＝</span><span lang=EN-US
style='mso-font-kerning:0pt'>1</span><span lang=ZH-CN style='mso-font-kerning:
0pt'>，</span><span lang=EN-US style='mso-font-kerning:0pt'>30</span><span
lang=ZH-CN style='mso-font-kerning:0pt'>，</span><span lang=EN-US
style='mso-font-kerning:0pt'>1</span><span lang=ZH-CN style='mso-font-kerning:
0pt'>”的意思是：</span><span lang=EN-US style='mso-font-kerning:0pt'>N</span><span
lang=ZH-CN style='mso-font-kerning:0pt'>的初值为</span><span lang=EN-US
style='mso-font-kerning:0pt'>1</span><span lang=ZH-CN style='mso-font-kerning:
0pt'>，终值为</span><span lang=EN-US style='mso-font-kerning:0pt'>30</span><span
lang=ZH-CN style='mso-font-kerning:0pt'>，每执行一次循环</span><span lang=EN-US
style='mso-font-kerning:0pt'>N</span><span lang=ZH-CN style='mso-font-kerning:
0pt'>的值增加</span><span lang=EN-US style='mso-font-kerning:0pt'>1</span><span
lang=ZH-CN style='mso-font-kerning:0pt'>。当</span><span lang=EN-US
style='mso-font-kerning:0pt'>N</span><span lang=ZH-CN style='mso-font-kerning:
0pt'>再变化到</span><span lang=EN-US style='mso-font-kerning:0pt'>31</span><span
lang=ZH-CN style='mso-font-kerning:0pt'>时，由于它已超过了指定的终值</span><span lang=EN-US
style='mso-font-kerning:0pt'>30</span><span lang=ZH-CN style='mso-font-kerning:
0pt'>，不再执行循环。</span><span lang=EN-US style='mso-font-kerning:0pt'><o:p></o:p></span></p>

<p class=MsoBodyTextIndent2 style='line-height:17.0pt;mso-line-height-rule:
exactly'><span lang=ZH-CN style='mso-font-kerning:0pt'>下面的</span><span
lang=EN-US style='mso-font-kerning:0pt'>DO</span><span lang=ZH-CN
style='mso-font-kerning:0pt'>语句是合法的：</span><span lang=EN-US style='mso-font-kerning:
0pt'><o:p></o:p></span></p>

<p class=MsoBodyTextIndent2 style='margin-left:42.5pt;mso-para-margin-left:
4.05gd;line-height:15.0pt;mso-line-height-rule:exactly'><span lang=EN-US
style='mso-font-kerning:0pt'>DO 10</span><span lang=ZH-CN style='mso-font-kerning:
0pt'>，</span><span lang=EN-US style='mso-font-kerning:0pt'>I=1</span><span
lang=ZH-CN style='mso-font-kerning:0pt'>，</span><span lang=EN-US
style='mso-font-kerning:0pt'>10</span><span lang=ZH-CN style='mso-font-kerning:
0pt'>，</span><span lang=EN-US style='mso-font-kerning:0pt'>2<o:p></o:p></span></p>

<p class=MsoBodyTextIndent2 style='margin-left:42.5pt;mso-para-margin-left:
4.05gd;line-height:15.0pt;mso-line-height-rule:exactly'><span lang=EN-US
style='mso-font-kerning:0pt'>DO 20 N=1</span><span lang=ZH-CN style='mso-font-kerning:
0pt'>，</span><span lang=EN-US style='mso-font-kerning:0pt'>5<o:p></o:p></span></p>

<p class=MsoBodyTextIndent2 style='margin-left:42.5pt;mso-para-margin-left:
4.05gd;line-height:15.0pt;mso-line-height-rule:exactly'><span lang=EN-US
style='mso-font-kerning:0pt'>DO 100</span><span lang=ZH-CN style='mso-font-kerning:
0pt'>，</span><span lang=EN-US style='mso-font-kerning:0pt'>X=1.2</span><span
lang=ZH-CN style='mso-font-kerning:0pt'>，</span><span lang=EN-US
style='mso-font-kerning:0pt'>2.4</span><span lang=ZH-CN style='mso-font-kerning:
0pt'>，</span><span lang=EN-US style='mso-font-kerning:0pt'>0.2<o:p></o:p></span></p>

<p class=MsoBodyTextIndent2 style='margin-left:42.5pt;mso-para-margin-left:
4.05gd;line-height:15.0pt;mso-line-height-rule:exactly'><span lang=EN-US
style='mso-font-kerning:0pt'>DO T</span><span lang=ZH-CN style='mso-font-kerning:
0pt'>＝</span><span lang=EN-US style='mso-font-kerning:0pt'>2.5*2</span><span
lang=ZH-CN style='mso-font-kerning:0pt'>，</span><span lang=EN-US
style='mso-font-kerning:0pt'>5O./3.</span><span lang=ZH-CN style='mso-font-kerning:
0pt'>，</span><span lang=EN-US style='mso-font-kerning:0pt'>0.3<o:p></o:p></span></p>

<p class=MsoBodyTextIndent2 style='margin-left:42.5pt;mso-para-margin-left:
4.05gd;line-height:15.0pt;mso-line-height-rule:exactly'><span lang=EN-US
style='mso-font-kerning:0pt'>DO M</span><span lang=ZH-CN style='mso-font-kerning:
0pt'>＝</span><span lang=EN-US style='mso-font-kerning:0pt'>1.5</span><span
lang=ZH-CN style='mso-font-kerning:0pt'>，</span><span lang=EN-US
style='mso-font-kerning:0pt'>12.5</span><span lang=ZH-CN style='mso-font-kerning:
0pt'>，</span><span lang=EN-US style='mso-font-kerning:0pt'>15<o:p></o:p></span></p>

<p class=MsoBodyTextIndent2 style='line-height:17.0pt;mso-line-height-rule:
exactly'><span lang=EN-US style='mso-font-kerning:0pt'>DO</span><span
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