📄 c语言基础(02-数据类型、运算符与表达式).htm
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<P align=center>作者：dd 教程来源：C语言之家 点击数：99 更新时间：2006-6-6 <A title=收藏的网页将被永久地保存到新浪ViVi收藏夹http://vivi.sina.com.cn href="javascript:d=document;t=d.selection?(d.selection.type!='None'?d.selection.createRange().text:''):(d.getSelection?d.getSelection():'');void(vivi=window.open('http://vivi.sina.com.cn/collect/icollect.php?pid=2008&title='+escape(d.title)+'&url='+escape(d.location.href)+'&desc='+escape(t),'vivi','scrollbars=no,width=480,height=480,left=75,top=20,status=no,resizable=yes'));vivi.focus();"><IMG src="/images/vivi_coop1.gif" align=absMiddle border=0></A> </P></td>
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<p align="left"><FONT color=#ff6600><FONT size=1> </FONT><B><SPAN style="FONT-SIZE: 14pt; COLOR: #ff6600; FONT-FAMILY: 宋体; mso-bidi-font-size: 12.0pt; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">数据类型、运算符与表达式</SPAN></B></FONT><B><SPAN lang=EN-US style="FONT-SIZE: 14pt; COLOR: #ff6600; mso-bidi-font-size: 12.0pt"><?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p></o:p></SPAN></B>
<P class=MsoNormal><SPAN lang=EN-US> <o:p></o:p></SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 27pt"><B><SPAN style="COLOR: blue; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">数据的类型：</SPAN><SPAN lang=EN-US style="COLOR: blue"><o:p></o:p></SPAN></B></P>
<P class=MsoNormal style="TEXT-INDENT: 27pt"><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">在程序中要处理大量的数据，把这些数据按其特点分为几种基本的数据类型，它们分别是：</SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 27pt"><SPAN lang=EN-US>1</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">、整型 </SPAN><SPAN lang=EN-US>2</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">、字符型 </SPAN><SPAN lang=EN-US>3</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">、实型</SPAN><SPAN lang=EN-US><o:p></o:p></SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 21pt; mso-char-indent-count: 2.0; mso-char-indent-size: 10.5pt"><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">还有其它的一些扩展的数据类型，但是开始学习时要先熟悉这三种基本数据类型。</SPAN><SPAN lang=EN-US><o:p></o:p></SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 21pt; mso-char-indent-count: 2.0; mso-char-indent-size: 10.5pt"><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">在</SPAN><SPAN lang=EN-US>C</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">语言中这几种数据类型用符号表示如下：</SPAN><SPAN lang=EN-US><o:p></o:p></SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 21pt; mso-char-indent-count: 2.0; mso-char-indent-size: 10.5pt"><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">整型数据类型 </SPAN><SPAN lang=EN-US>int</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"> </SPAN><SPAN lang=EN-US>/*</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">一般指可以运算的数，如自然数就是整型数据类型</SPAN><SPAN lang=EN-US>*/<o:p></o:p></SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 21pt; mso-char-indent-count: 2.0; mso-char-indent-size: 10.5pt"><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">字符数据类型 </SPAN><SPAN lang=EN-US>char</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"> </SPAN><SPAN lang=EN-US>/*</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">一般指文字，如英文字母；字符类型的</SPAN><SPAN lang=EN-US>’1’’2’’3’’4’</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">等</SPAN><SPAN lang=EN-US>*/<o:p></o:p></SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 21pt; mso-char-indent-count: 2.0; mso-char-indent-size: 10.5pt"><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">实型</SPAN><SPAN lang=EN-US><SPAN style="mso-spacerun: yes"> </SPAN>float<SPAN style="mso-spacerun: yes"> </SPAN>/*</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">也称作浮点型，记住</SPAN><SPAN lang=EN-US>float</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">类型的数都是有小数位的，如</SPAN><SPAN lang=EN-US>425.23*/<o:p></o:p></SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 21pt; mso-char-indent-count: 2.0; mso-char-indent-size: 10.5pt"><SPAN lang=EN-US> <o:p></o:p></SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 21.1pt; mso-char-indent-count: 2.0; mso-char-indent-size: 10.55pt"><B><SPAN style="COLOR: blue; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">常量和变量：</SPAN><SPAN lang=EN-US style="COLOR: blue"><o:p></o:p></SPAN></B></P>
<P class=MsoNormal style="TEXT-INDENT: 21pt; mso-char-indent-count: 2.0; mso-char-indent-size: 10.5pt"><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">常量――程序运行过程中其值不变的量，如一个整数</SPAN><SPAN lang=EN-US style="COLOR: black">134,</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"> 一个字符</SPAN><SPAN lang=EN-US style="COLOR: black"> ‘a’<o:p></o:p></SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 21pt; mso-char-indent-count: 2.0; mso-char-indent-size: 10.5pt"><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">变量――程序运行过程中其值可以变化的量，如 </SPAN><SPAN lang=EN-US style="COLOR: black">int a;<SPAN style="mso-spacerun: yes"> </SPAN>char<SPAN style="mso-spacerun: yes"> </SPAN>b; </SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">那么</SPAN><SPAN lang=EN-US style="COLOR: black">a </SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">和</SPAN><SPAN lang=EN-US style="COLOR: black">b</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"> 都是变量。</SPAN><SPAN lang=EN-US style="COLOR: black"><o:p></o:p></SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 21pt; mso-char-indent-count: 2.0; mso-char-indent-size: 10.5pt"><SPAN lang=EN-US style="COLOR: black"> <o:p></o:p></SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 21.1pt; mso-char-indent-count: 2.0; mso-char-indent-size: 10.55pt"><B><SPAN style="COLOR: blue; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">符号常量</SPAN></B><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">――用一个“符号”来表示的一个“常量”称为“符号常量”。</SPAN><SPAN lang=EN-US style="COLOR: black"><o:p></o:p></SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 21pt; mso-char-indent-count: 2.0; mso-char-indent-size: 10.5pt"><SPAN style="COLOR: blue; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">符号常量有什么好处</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">――在给符号常量命名的时候，按习惯取的名字与实际上的含义相符，可以“见名识意”；另外在需要修改常量的值的时候，只需要修改符号常量的定义部分即可，非常方便。</SPAN><SPAN lang=EN-US style="COLOR: black"><o:p></o:p></SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 21pt; mso-char-indent-count: 2.0; mso-char-indent-size: 10.5pt"><SPAN style="COLOR: blue; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">符号常量的定义方法</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">――</SPAN><SPAN lang=EN-US style="COLOR: black">#define<SPAN style="mso-spacerun: yes"> </SPAN></SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">符号 常量 </SPAN><SPAN lang=EN-US style="COLOR: black"><o:p></o:p></SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 21pt; mso-char-indent-count: 2.0; mso-char-indent-size: 10.5pt"><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">例：</SPAN><SPAN lang=EN-US style="COLOR: black">#define<SPAN style="mso-spacerun: yes"> </SPAN>NUMBER 30<SPAN style="mso-spacerun: yes"> </SPAN>/*</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">定义了一个符号常量，在这里是用符号</SPAN><SPAN lang=EN-US style="COLOR: black">NUMBER</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"> 表示整数</SPAN><SPAN lang=EN-US style="COLOR: black">30</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">，以后在程序里就可以</SPAN><SPAN lang=EN-US style="COLOR: black"><o:p></o:p></SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 178.5pt; mso-char-indent-count: 17.0; mso-char-indent-size: 10.5pt"><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">用符号</SPAN><SPAN lang=EN-US style="COLOR: black">NUMBER</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"> 代替整数</SPAN><SPAN lang=EN-US style="COLOR: black">30</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">进行运算</SPAN><SPAN lang=EN-US style="COLOR: black">*/<o:p></o:p></SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 21pt"><SPAN lang=EN-US style="COLOR: black">main()<o:p></o:p></SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 21pt"><SPAN lang=EN-US style="COLOR: black">{<SPAN style="mso-spacerun: yes"> </SPAN><o:p></o:p></SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 21pt"><SPAN lang=EN-US style="COLOR: black"><SPAN style="mso-spacerun: yes"> </SPAN>int a=20;</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"> </SPAN><SPAN lang=EN-US style="COLOR: black">/*</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">把常量</SPAN><SPAN lang=EN-US style="COLOR: black">20</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">赋给整型变量</SPAN><SPAN lang=EN-US style="COLOR: black">a*/<o:p></o:p></SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 21pt"><SPAN lang=EN-US style="COLOR: black"><SPAN style="mso-spacerun: yes"> </SPAN>int c;</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"> </SPAN><SPAN lang=EN-US style="COLOR: black">/*</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">定义了整型变量</SPAN><SPAN lang=EN-US style="COLOR: black">c*/<o:p></o:p></SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 21pt"><SPAN lang=EN-US style="COLOR: black"><SPAN style="mso-spacerun: yes"> </SPAN>c=NUMBER+a;<SPAN style="mso-spacerun: yes"> </SPAN>/*</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">变量</SPAN><SPAN lang=EN-US style="COLOR: black">c</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">的值此时为</SPAN><SPAN lang=EN-US style="COLOR: black"> 50</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">，符号常量</SPAN><SPAN lang=EN-US style="COLOR: black">NUMBER</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">参与了运算</SPAN><SPAN lang=EN-US style="COLOR: black">*/<o:p></o:p></SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 21pt"><SPAN lang=EN-US style="COLOR: black">}<o:p></o:p></SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 21pt"><SPAN lang=EN-US style="COLOR: black"> <o:p></o:p></SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 21pt"><SPAN style="COLOR: blue; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">变量的定义方法</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">――在变量的名字前面加上一个变量的数据类型，以说明已定义的变量可以用来存放什么样类型的数据。</SPAN><SPAN lang=EN-US style="COLOR: black"><o:p></o:p></SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 21pt"><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">例： </SPAN><SPAN lang=EN-US style="COLOR: black">int<SPAN style="mso-spacerun: yes"> </SPAN>a;<SPAN style="mso-spacerun: yes"> </SPAN>/*</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">定义了一个整型变量，以后这个变量只能存放整型类型的数</SPAN><SPAN lang=EN-US style="COLOR: black">*/<o:p></o:p></SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 21pt"><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"> </SPAN><SPAN lang=EN-US style="COLOR: black">char b;<SPAN style="mso-spacerun: yes"> </SPAN>/*</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">定义了一个字符型变量，以后这个变量只能存放符字符型数据</SPAN><SPAN lang=EN-US style="COLOR: black">*/<o:p></o:p></SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 21pt"><SPAN style="COLOR: blue; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">怎样把常量值赋给已定义了的变量</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">――用一个</SPAN><SPAN lang=EN-US style="COLOR: black"> = </SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">号赋值。</SPAN><SPAN lang=EN-US style="COLOR: black"><o:p></o:p></SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 21pt"><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">例： </SPAN><SPAN lang=EN-US style="COLOR: black">int<SPAN style="mso-spacerun: yes"> </SPAN>a;<SPAN style="mso-spacerun: yes"> </SPAN>/*</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">定义一个整型娈量</SPAN><SPAN lang=EN-US style="COLOR: black">a*/<o:p></o:p></SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 42pt; mso-char-indent-count: 4.0; mso-char-indent-size: 10.5pt"><SPAN lang=EN-US style="COLOR: black"><SPAN style="mso-spacerun: yes"> </SPAN>char b;<SPAN style="mso-spacerun: yes"> </SPAN>/*</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">定义了一个字符型变量</SPAN><SPAN lang=EN-US style="COLOR: black">b*/<o:p></o:p></SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 52.5pt; mso-char-indent-count: 5.0; mso-char-indent-size: 10.5pt"><SPAN lang=EN-US style="COLOR: black">a=20;<SPAN style="mso-spacerun: yes"> </SPAN>/*</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">用 </SPAN><SPAN lang=EN-US style="COLOR: black">=<SPAN style="mso-spacerun: yes"> </SPAN></SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">号完成赋值，赋值后变量</SPAN><SPAN lang=EN-US style="COLOR: black">a</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">的值此时为</SPAN><SPAN lang=EN-US style="COLOR: black"> 20*/<o:p></o:p></SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 52.5pt; mso-char-indent-count: 5.0; mso-char-indent-size: 10.5pt"><SPAN lang=EN-US style="COLOR: black">b=’d’<SPAN style="mso-spacerun: yes"> </SPAN>/*</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">把常量字符</SPAN><SPAN lang=EN-US style="COLOR: black">’d’</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">赋给变量</SPAN><SPAN lang=EN-US style="COLOR: black">b</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">，此时变量</SPAN><SPAN lang=EN-US style="COLOR: black">b</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">的值是字符</SPAN><SPAN lang=EN-US style="COLOR: black">’d’*/<o:p></o:p></SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 21pt"><SPAN style="COLOR: blue; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">变量赋值时一种更灵活的方法</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">――可以在一行上给多个相同数据类型的变量赋值，变量之间用逗号分隔。</SPAN><SPAN lang=EN-US style="COLOR: black"><o:p></o:p></SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 21pt"><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">例：</SPAN><SPAN lang=EN-US style="COLOR: black"> int a,b,c,d;<SPAN style="mso-spacerun: yes"> </SPAN>/*</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">定义了</SPAN><SPAN lang=EN-US style="COLOR: black">4</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">个整型变量</SPAN><SPAN lang=EN-US style="COLOR: black">*/<o:p></o:p></SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 21pt"><SPAN lang=EN-US style="COLOR: black"><SPAN style="mso-spacerun: yes"> </SPAN>char<SPAN style="mso-spacerun: yes"> </SPAN>e,f,g;</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"> </SPAN><SPAN lang=EN-US style="COLOR: black">/*</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">定义了</SPAN><SPAN lang=EN-US style="COLOR: black">3</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">个字符型变量</SPAN><SPAN lang=EN-US style="COLOR: black">*/<o:p></o:p></SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 21pt"><SPAN style="COLOR: blue; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">深入理解变量</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">――</SPAN><SPAN lang=EN-US style="COLOR: black">1</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">）</SPAN><SPAN lang=EN-US style="COLOR: black">1</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">个变量必须有一个变量名。 </SPAN><SPAN lang=EN-US style="COLOR: black">2</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">）变量必须有其指定的数据类型</SPAN><SPAN lang=EN-US style="COLOR: black"><o:p></o:p></SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 21pt"><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"> </SPAN><SPAN lang=EN-US style="COLOR: black">3</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">）变量一旦被定义，它就在内存中占有一个位置，这个位置称做该</SPAN><SPAN style="COLOR: red; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">变量的地址</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">。</SPAN><SPAN lang=EN-US style="COLOR: black"><o:p></o:p></SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 21pt"><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"> </SPAN><SPAN lang=EN-US style="COLOR: black">4</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">）每一个变量都有其对应的值。</SPAN><SPAN lang=EN-US style="COLOR: black"><o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 39pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo4; tab-stops: list 39.0pt"><SPAN lang=EN-US style="COLOR: black; FONT-FAMILY: Wingdings">l<SPAN style="FONT: 7pt 'Times New Roman'"> </SPAN></SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">一定要牢记变量的这</SPAN><SPAN lang=EN-US style="COLOR: black">4</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">个特性。</SPAN><SPAN lang=EN-US style="COLOR: black"><o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 21pt"><SPAN style="COLOR: blue; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">变量使用时的注意事项</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">――</SPAN><SPAN lang=EN-US style="COLOR: black">1</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">）变量在使用之前一定要先定义，使用一个没有定义的变量是错误的。</SPAN><SPAN lang=EN-US style="COLOR: black"><o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 21pt"><SPAN style="COLOR: blue; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"> </SPAN><SPAN lang=EN-US style="COLOR: black">2</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">）变量必须在一个函数的开始部分定义。（这个限制在</SPAN><SPAN lang=EN-US style="COLOR: black">C++</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">中不存在）</SPAN><SPAN lang=EN-US style="COLOR: black"><o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 21pt"><SPAN lang=EN-US style="COLOR: black"> <o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 21pt"><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">例题：写一个</SPAN><SPAN lang=EN-US style="COLOR: black">2</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">个整数相加的程序。</SPAN><SPAN lang=EN-US style="COLOR: black"><o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 21pt"><SPAN lang=EN-US style="COLOR: black">/*</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">解题思路：求</SPAN><SPAN lang=EN-US style="COLOR: black">2</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">个整数相加，必定要先定义</SPAN><SPAN lang=EN-US style="COLOR: black">2</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">个变量来存放这</SPAN><SPAN lang=EN-US style="COLOR: black">2</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">个数，另外还需要</SPAN><SPAN lang=EN-US style="COLOR: black">1</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">个变量用来存放</SPAN><SPAN lang=EN-US style="COLOR: black"><o:p></o:p></SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 10.5pt; mso-char-indent-count: 1.0; mso-char-indent-size: 10.5pt"><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">相加的和，所以共需要定义</SPAN><SPAN lang=EN-US style="COLOR: black">3</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">个整型变量</SPAN><SPAN lang=EN-US style="COLOR: black">*/<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"> </SPAN><SPAN lang=EN-US style="COLOR: black">/*</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">注意每次在写</SPAN><SPAN lang=EN-US style="COLOR: black">C</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">程序的时候一定要注意书写格式</SPAN><SPAN lang=EN-US style="COLOR: black">*/<o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 21pt"><SPAN lang=EN-US style="COLOR: black">main()<o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 21pt"><SPAN lang=EN-US style="COLOR: black">{<o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 21pt"><SPAN lang=EN-US style="COLOR: black"><SPAN style="mso-spacerun: yes"> </SPAN>int a,b,c;<SPAN style="mso-spacerun: yes"> </SPAN><o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 21pt"><SPAN lang=EN-US style="COLOR: black"><SPAN style="mso-spacerun: yes"> </SPAN>a=20,b=30;<SPAN style="mso-spacerun: yes"> </SPAN>/*</SPAN><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">在这里指定变量的值，因为还没有讲输入输出函数，只能这样了。</SPAN><SPAN lang=EN-US style="COLOR: black">*/<o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 21pt"><SPAN lang=EN-US style="COLOR: black"><SPAN style="mso-spacerun: yes"> </SPAN>c=a+b;<o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 21pt"><SPAN lang=EN-US style="COLOR: black">}<o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 21pt"><SPAN lang=EN-US style="COLOR: black"> <o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 21pt"><SPAN style="COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">想一想，这样简单的一个题，需要知道的知识面却不少。</SPAN><SPAN style="COLOR: red; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">用到了上面所讲的哪些知识？</SPAN><SPAN lang=EN-US style="COLOR: red"><o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 21pt"><SPAN lang=EN-US style="COLOR: red"> <o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 21pt"><SPAN lang=EN-US style="COLOR: black"> <o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 21pt"><SPAN style="COLOR: blue; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">作业题：</SPAN><SPAN lang=EN-US style="COLOR: blue"><o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 21pt"><SPAN style="COLOR: blue; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">编程求一个数，这个数是</SPAN><SPAN lang=EN-US style="COLOR: blue">6</SPAN><SPAN style="COLOR: blue; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">的</SPAN><SPAN lang=EN-US style="COLOR: blue">5</SPAN><SPAN style="COLOR: blue; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"> 倍。</SPAN><SPAN lang=EN-US style="COLOR: blue"><o:p></o:p></SPAN></P> </td>
</tr>
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