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lang=EN-US style='font-size:12.0pt;font-family:宋体;color:#333399'>[</span><span
lang=ZH-CN style='font-size:12.0pt;font-family:宋体;color:#333399'>例</span><span
lang=EN-US style='font-size:12.0pt;font-family:宋体;color:#333399'>1.5] </span><span
lang=ZH-CN style='font-size:12.0pt;font-family:宋体;color:#333399'>函数的计算。</span><span
lang=EN-US style='font-size:12.0pt;font-family:宋体'>[<a
href="example/e_121_05.f90">e_121_05.f90</a>]</span><span lang=EN-US
style='font-size:12.0pt;font-family:宋体;mso-font-kerning:0pt'><o:p></o:p></span></p>
<p class=MsoNormal style='tab-stops:45.8pt 91.6pt 137.4pt 183.2pt 229.0pt 274.8pt 320.6pt 366.4pt 412.2pt 458.0pt 503.8pt 549.6pt 595.4pt 641.2pt 687.0pt 732.8pt'><span
lang=EN-US style='font-size:12.0pt;font-family:宋体;color:#333399'>[</span><span
lang=ZH-CN style='font-size:12.0pt;font-family:宋体;color:#333399'>例</span><span
lang=EN-US style='font-size:12.0pt;font-family:宋体;color:#333399'>1.6] </span><span
lang=ZH-CN style='font-size:12.0pt;font-family:宋体;color:#333399'>分别求半径</span><span
lang=EN-US style='font-size:12.0pt;font-family:宋体;color:#333399'>R=1</span><span
lang=ZH-CN style='font-size:12.0pt;font-family:宋体;color:#333399'>，</span><span
lang=EN-US style='font-size:12.0pt;font-family:宋体;color:#333399'>3</span><span
lang=ZH-CN style='font-size:12.0pt;font-family:宋体;color:#333399'>，</span><span
lang=EN-US style='font-size:12.0pt;font-family:宋体;color:#333399'>12.5</span><span
lang=ZH-CN style='font-size:12.0pt;font-family:宋体;color:#333399'>时的圆周长。此源程序由二部分组成：主程序和子程序。</span><span
lang=EN-US style='font-size:12.0pt;font-family:宋体'>[<a
href="example/e_121_06.f90">e_121_06.f90</a>]</span><span lang=EN-US
style='font-size:12.0pt;font-family:宋体;mso-font-kerning:0pt'><o:p></o:p></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;
tab-stops:45.8pt 91.6pt 137.4pt 183.2pt 229.0pt 274.8pt 320.6pt 366.4pt 412.2pt 458.0pt 503.8pt 549.6pt 595.4pt 641.2pt 687.0pt 732.8pt'><a
name="第1_2_2"><span lang=EN-US style='font-size:16.0pt;mso-bidi-font-size:12.0pt;
mso-fareast-font-family:楷体_GB2312'>1.2.2</span></a><span style='mso-bookmark:
第1_2_2'></span><span lang=EN-US style='font-family:宋体'> </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'>Fortran</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'>程序的特点</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=MsoNormal style='text-indent:24.0pt;mso-char-indent-count:2.0;
line-height:18.0pt;mso-line-height-rule:exactly;tab-stops:45.8pt 91.6pt 137.4pt 183.2pt 229.0pt 274.8pt 320.6pt 366.4pt 412.2pt 458.0pt 503.8pt 549.6pt 595.4pt 641.2pt 687.0pt 732.8pt;
mso-char-indent-size:10.5pt'><span lang=ZH-CN style='font-size:12.0pt;
font-family:宋体'>从以上例子中可以看到：</span><span lang=EN-US style='font-size:12.0pt;
font-family:宋体'><o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:48.0pt;text-indent:-24.0pt;line-height:
18.0pt;mso-line-height-rule:exactly;mso-list:l2 level1 lfo4;tab-stops:list 48.0pt'><![if !supportLists]><span
lang=EN-US style='font-size:12.0pt;font-family:Symbol;mso-fareast-font-family:
Symbol;mso-bidi-font-family:Symbol'><span style='mso-list:Ignore'><img
width=13 height=13 src="Sec1-2.files/image001.gif" alt="*"><span
style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]><span lang=ZH-CN style='font-size:12.0pt;
font-family:宋体'>一个</span><span lang=EN-US style='font-size:12.0pt;font-family:
宋体'>Fortran</span><span lang=ZH-CN style='font-size:12.0pt;font-family:宋体'>程序由一个或若干个程序单位组成。<span
style='color:#CC00FF'>主程序</span>和<span style='color:#CC00FF'>辅程序</span>分别是一个独立的程序单位。主程序单元起整体控制作用，各辅程序单元完成总问题中的一个子问题。</span><span
lang=EN-US style='font-size:12.0pt;font-family:宋体'><o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:48.0pt;text-indent:-24.0pt;line-height:
18.0pt;mso-line-height-rule:exactly;mso-list:l2 level1 lfo4;tab-stops:list 48.0pt'><![if !supportLists]><span
lang=EN-US style='font-size:12.0pt;font-family:Symbol;mso-fareast-font-family:
Symbol;mso-bidi-font-family:Symbol'><span style='mso-list:Ignore'><img
width=13 height=13 src="Sec1-2.files/image001.gif" alt="*"><span
style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]><span lang=ZH-CN style='font-size:12.0pt;
font-family:宋体'>每一个程序单位都是以</span><span lang=EN-US style='font-size:12.0pt;
font-family:宋体'>END</span><span lang=ZH-CN style='font-size:12.0pt;font-family:
宋体'>语句结束的。</span><span lang=EN-US style='font-size:12.0pt;font-family:宋体'>END</span><span
lang=ZH-CN style='font-size:12.0pt;font-family:宋体'>既是一个程序单位的结束标志，又是一个独立的语句</span><span
lang=EN-US style='font-size:12.0pt;font-family:宋体'>(</span><span lang=ZH-CN
style='font-size:12.0pt;font-family:宋体'>结束语句</span><span lang=EN-US
style='font-size:12.0pt;font-family:宋体'>)</span><span lang=ZH-CN
style='font-size:12.0pt;font-family:宋体'>。主程序中的</span><span lang=EN-US
style='font-size:12.0pt;font-family:宋体'>END</span><span lang=ZH-CN
style='font-size:12.0pt;font-family:宋体'>语句的作用是使程序“停止运行”。辅程序中的</span><span
lang=EN-US style='font-size:12.0pt;font-family:宋体'>END</span><span lang=ZH-CN
style='font-size:12.0pt;font-family:宋体'>语句是“使流程返回调用程序”。</span><span lang=EN-US
style='font-size:12.0pt;font-family:宋体'><o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:48.0pt;text-indent:-24.0pt;line-height:
18.0pt;mso-line-height-rule:exactly;mso-list:l2 level1 lfo4;tab-stops:list 48.0pt'><![if !supportLists]><span
lang=EN-US style='font-size:12.0pt;font-family:Symbol;mso-fareast-font-family:
Symbol;mso-bidi-font-family:Symbol'><span style='mso-list:Ignore'><img
width=13 height=13 src="Sec1-2.files/image001.gif" alt="*"><span
style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]><span lang=ZH-CN style='font-size:12.0pt;
font-family:宋体'>一个程序单位包括若干行。</span><span lang=EN-US style='font-size:12.0pt;
font-family:宋体'><o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:65.55pt;text-indent:-17.1pt;line-height:
18.0pt;mso-line-height-rule:exactly;mso-list:l0 level1 lfo6;tab-stops:65.55pt 137.4pt 183.2pt 229.0pt 274.8pt 320.6pt 366.4pt 412.2pt 458.0pt 503.8pt 549.6pt 595.4pt 641.2pt 687.0pt 732.8pt;
mso-char-indent-size:12pt'><![if !supportLists]><span lang=EN-US
style='font-size:12.0pt;font-family:Symbol;mso-fareast-font-family:Symbol;
mso-bidi-font-family:Symbol'><span style='mso-list:Ignore'><img width=13
height=13 src="Sec1-2.files/image002.gif" alt="*"><span style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]><span lang=EN-US style='font-size:12.0pt;
font-family:宋体'>F77</span><span lang=ZH-CN style='font-size:12.0pt;font-family:
宋体'>行分为下面两类。</span><span lang=EN-US style='font-size:12.0pt;font-family:宋体'>F77</span><span
lang=ZH-CN style='font-size:12.0pt;font-family:宋体'>规定，一行只能写一个语句，一行中不能写几个语句。如果一个语句太长，一行内写不下的话，可以写在<span
style='color:#CC00FF'>继续行</span></span><span lang=EN-US style='font-size:12.0pt;
font-family:宋体'>(</span><span lang=ZH-CN style='font-size:12.0pt;font-family:
宋体'>要用“续行标志”</span><span lang=EN-US style='font-size:12.0pt;font-family:宋体'>)<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:79.8pt;text-indent:-17.1pt;line-height:
17.0pt;mso-line-height-rule:exactly;mso-list:l3 level1 lfo8;tab-stops:79.5pt 105.45pt 137.4pt 183.2pt 229.0pt 274.8pt 320.6pt 366.4pt 412.2pt 458.0pt 503.8pt 549.6pt 595.4pt 641.2pt 687.0pt 732.8pt'><![if !supportLists]><span
lang=EN-US style='font-size:12.0pt;font-family:Symbol;mso-fareast-font-family:
Symbol;mso-bidi-font-family:Symbol'><span style='mso-list:Ignore'><img
width=13 height=13 src="Sec1-2.files/image003.gif" alt="*"><span
style='font:7.0pt "Times New Roman"'> </span></span></span><![endif]><span
lang=ZH-CN style='font-size:12.0pt;font-family:宋体;color:#CC00FF'>语句行</span><span
lang=ZH-CN style='font-size:12.0pt;font-family:宋体'>。由一个</span><span lang=EN-US
style='font-size:12.0pt;font-family:宋体'>Fortran</span><span lang=ZH-CN
style='font-size:12.0pt;font-family:宋体'>语句组成， </span><span lang=EN-US
style='font-size:12.0pt;font-family:宋体'>Fortran</span><span lang=ZH-CN
style='font-size:12.0pt;font-family:宋体'>语句分为执行语句和非执行语句。<span style='color:#CC00FF'>执行语句</span>使计算机在运行时产生某些操作，如赋值语句、打印语句等。<span
style='color:#CC00FF'>非执行语句</span></span><span lang=EN-US style='font-size:
12.0pt;font-family:宋体'>(</span><span lang=ZH-CN style='font-size:12.0pt;
font-family:宋体'>包括说明语句，数据语句等</span><span lang=EN-US style='font-size:12.0pt;
font-family:宋体'>)</span><span lang=ZH-CN style='font-size:12.0pt;font-family:
宋体'>将有关信息通知编译系统，以便在编译时作出相应的处理，例如类型说明语句、函数子程序语句等。</span><span lang=EN-US
style='font-size:12.0pt;font-family:宋体'>Fortran</span><span lang=ZH-CN
style='font-size:12.0pt;font-family:宋体'>程序的基本成份是语句。</span><span lang=EN-US
style='font-size:12.0pt;font-family:宋体'><o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:79.8pt;text-indent:-17.1pt;line-height:
17.0pt;mso-line-height-rule:exactly;mso-list:l3 level1 lfo8;tab-stops:79.5pt 105.45pt 137.4pt 183.2pt 229.0pt 274.8pt 320.6pt 366.4pt 412.2pt 458.0pt 503.8pt 549.6pt 595.4pt 641.2pt 687.0pt 732.8pt;
mso-char-indent-size:12pt'><![if !supportLists]><span lang=EN-US
style='font-size:12.0pt;font-family:Symbol;mso-fareast-font-family:Symbol;
mso-bidi-font-family:Symbol'><span style='mso-list:Ignore'><img width=13
height=13 src="Sec1-2.files/image003.gif" alt="*"><span style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]><span lang=ZH-CN style='font-size:12.0pt;
font-family:宋体;color:#CC00FF'>非语句行，即注释行</span><span lang=ZH-CN
style='font-size:12.0pt;font-family:宋体'>。它不是</span><span lang=EN-US
style='font-size:12.0pt;font-family:宋体'>Fortran</span><span lang=ZH-CN
style='font-size:12.0pt;font-family:宋体'>语句，它不被翻译成机器目标指令。不产生任何机器操作。它仅仅是为了人们阅读程序的方便而加到程序中的。一个程序中注释行的数目不受限制，根据需要而定。但一个程序单位不能只由注释行组成。注释行的内容完全是根据程序设计人员需要而写的，一般是为程序</span><span
lang=EN-US style='font-size:12.0pt;font-family:宋体'>(</span><span lang=ZH-CN
style='font-size:12.0pt;font-family:宋体'>或程序中一部分</span><span lang=EN-US
style='font-size:12.0pt;font-family:宋体'>)</span><span lang=ZH-CN
style='font-size:12.0pt;font-family:宋体'>的作用作注释以易于理解程序。</span><span lang=EN-US
style='font-size:12.0pt;font-family:宋体'><o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:65.55pt;text-indent:-17.1pt;line-height:
18.0pt;mso-line-height-rule:exactly;mso-list:l0 level1 lfo6;tab-stops:65.55pt 137.4pt 183.2pt 229.0pt 274.8pt 320.6pt 366.4pt 412.2pt 458.0pt 503.8pt 549.6pt 595.4pt 641.2pt 687.0pt 732.8pt;
mso-char-indent-size:12pt'><![if !supportLists]><span lang=EN-US
style='font-size:12.0pt;font-family:Symbol;mso-fareast-font-family:Symbol;
mso-bidi-font-family:Symbol'><span style='mso-list:Ignore'><img width=13
height=13 src="Sec1-2.files/image002.gif" alt="*"><span style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]><span lang=EN-US style='font-size:12.0pt;
font-family:宋体'>F90</span><span lang=ZH-CN style='font-size:12.0pt;font-family:
宋体'>行不分类。注释可以写在任一行末尾，而且一行不限语句数，可以将几个</span><span lang=EN-US style='font-size:
12.0pt;font-family:宋体'>F77</span><span lang=ZH-CN style='font-size:12.0pt;
font-family:宋体'>行合并写入一行。这样，极大地简化了程序写法，使得程序可以编写得更为清晰明了。因此</span><span
lang=EN-US style='font-size:12.0pt;font-family:宋体'>F90</span><span lang=ZH-CN
style='font-size:12.0pt;font-family:宋体'>的格式较</span><span lang=EN-US
style='font-size:12.0pt;font-family:宋体'>F77</span><span lang=ZH-CN
style='font-size:12.0pt;font-family:宋体'>有柔软性。</span><span lang=EN-US
style='font-size:12.0pt;font-family:宋体'><o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:48.0pt;text-indent:-24.0pt;line-height:
18.0pt;mso-line-height-rule:exactly;mso-list:l2 level1 lfo4;tab-stops:list 48.0pt'><![if !supportLists]><span
lang=EN-US style='font-size:12.0pt;font-family:Symbol;mso-fareast-font-family:
Symbol;mso-bidi-font-family:Symbol'><span style='mso-list:Ignore'><img
width=13 height=13 src="Sec1-2.files/image001.gif" alt="*"><span
style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]><span lang=EN-US style='font-size:12.0pt;
font-family:宋体'>Fortran</span><span lang=ZH-CN style='font-size:12.0pt;
font-family:宋体'>程序中的语句可以有标号。一个语句有否标号是根据需要而定，其作用是标志一个语句以便被其它语句引用。在同一个程序单元中不能有两个相同标号的语句。标号不影响语句的执行顺序。但在</span><span
lang=EN-US style='font-size:12.0pt;font-family:宋体'>F90</span><span lang=ZH-CN
style='font-size:12.0pt;font-family:宋体'>中因为提倡结构化程序设计，一般不使用标号。</span><span
lang=EN-US style='font-size:12.0pt;font-family:宋体'><o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:48.0pt;text-indent:-24.0pt;line-height:
18.0pt;mso-line-height-rule:exactly;mso-list:l2 level1 lfo4;tab-stops:list 48.0pt'><![if !supportLists]><span
lang=EN-US style='font-size:12.0pt;font-family:Symbol;mso-fareast-font-family:
Symbol;mso-bidi-font-family:Symbol'><span style='mso-list:Ignore'><img
width=13 height=13 src="Sec1-2.files/image001.gif" alt="*"><span
style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]><span lang=ZH-CN style='font-size:12.0pt;
font-family:宋体'>一个程序单位中各类语句的位置是有一定规定的。例如</span><span lang=EN-US
style='font-size:12.0pt;font-family:宋体'>PROGRAM</span><span lang=ZH-CN
style='font-size:12.0pt;font-family:宋体'>语句应是主程序的第一个语句。</span><span lang=EN-US
style='font-size:12.0pt;font-family:宋体'>FUNCTION</span><span lang=ZH-CN
style='font-size:12.0pt;font-family:宋体'>语句是函数子程序的第一个语句，</span><span lang=EN-US
style='font-size:12.0pt;font-family:宋体'>END</span><span lang=ZH-CN
style='font-size:12.0pt;font-family:宋体'>语句只能是程序单位中最后一行。程序中语句执行的顺序一般依照它们在程序中的先后位置而定。</span><span
lang=EN-US style='font-size:12.0pt;font-family:宋体'><o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:48.0pt;text-indent:-24.0pt;line-height:
18.0pt;mso-line-height-rule:exactly;mso-list:l2 level1 lfo4;tab-stops:list 48.0pt'><![if !supportLists]><span
lang=EN-US style='font-size:12.0pt;font-family:Symbol;mso-fareast-font-family:
Symbol;mso-bidi-font-family:Symbol'><span style='mso-list:Ignore'><img
width=13 height=13 src="Sec1-2.files/image001.gif" alt="*"><span
style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]><span lang=EN-US style='font-size:12.0pt;
font-family:宋体'>F77</span><span lang=ZH-CN style='font-size:12.0pt;font-family:
宋体'>源程序必须按固定格式书写，即源程序中哪些内容应写在一行中的哪一列</span><span lang=EN-US style='font-size:
12.0pt;font-family:宋体'>(</span><span lang=ZH-CN style='font-size:12.0pt;
font-family:宋体'>或哪几列上</span><span lang=EN-US style='font-size:12.0pt;
font-family:宋体'>)</span><span lang=ZH-CN style='font-size:12.0pt;font-family:
宋体'>有严格的规定。而</span><span lang=EN-US style='font-size:12.0pt;font-family:宋体'>F90</span><span
lang=ZH-CN style='font-size:12.0pt;font-family:宋体'>可采用自由格式。</span><span
lang=EN-US style='font-size:12.0pt;font-family:宋体'><o:p></o:p></span></p>
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