chapter4.htm

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  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">5、初始化的近程数据段</font></p>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">格式：.DATA</font></p>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">隐含段名为@DATA，定位类型为WORD，</font></p>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">组合类型为PUBLIC，类别标志符为‘DATA’</font></p>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">6、未初始化的近程数据段</font></p>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">格式：.DATA？</font></p>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">隐含段名为@DATA？，定位类型为WORD，</font></p>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">组合类型为PUBLIC，类别标志符为‘BSS’</font></p>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">7、常数段</font></p>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">格式：.CONST</font></p>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">隐含段名为@CONST。</font></p>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">8、隐含的GROUP操作</font></p>
  <blockquote>
    <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">DGROUP GROUP @DATA，@CONST，@DATA？，@STACK</font></p>
  </blockquote>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">9、隐含的ASSUME操作</font></p>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">小模式/压缩模式：</font></p>
  <blockquote>
    <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">ASSUME&nbsp; CS：@CODE，DS：DGROUP，SS：DGROUP</font></p>
  </blockquote>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">&nbsp;&nbsp;&nbsp; </font><font
  face="宋体" size="5" color="#FFFF00">当不与高级语言连接时，可以不区分初始化的、未初始化的变量和常数数据，都可以在 
  .DATA中使用。</font></p>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">例如：</font></p>
  <blockquote>
    <blockquote>
      <blockquote>
        <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">DOSSEG</font></p>
        <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">.MODEL&nbsp; SMALL</font></p>
        <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">.STACK</font></p>
        <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">.DATA</font></p>
        <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">MSG&nbsp; DB &nbsp; “HELLO,WORLD”,‘$’</font></p>
        <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">.CODE</font></p>
      </blockquote>
    </blockquote>
    <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">START：MOV&nbsp; AX，DGROUP</font></p>
    <blockquote>
      <blockquote>
        <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">MOV&nbsp; DS，AX</font></p>
        <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">LEA&nbsp;&nbsp; DX，MSG</font></p>
        <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">MOV&nbsp; AH，9</font></p>
        <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">INT&nbsp;&nbsp; 21H</font></p>
        <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">MOV&nbsp; AX，4C00H</font></p>
        <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">INT&nbsp;&nbsp; 21H</font></p>
        <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">END&nbsp; START</font></p>
      </blockquote>
    </blockquote>
  </blockquote>
</blockquote>

<h3 align="left"><font FACE="宋体" size="5" color="#FFFFFF">七、指定地址</font></h3>

<blockquote>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">1、指定初始地址</font></p>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">格式：ORG&nbsp; 表达式</font></p>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">例如：</font></p>
  <blockquote>
    <blockquote>
      <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">ORG&nbsp; 100H</font></p>
    </blockquote>
  </blockquote>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">2、地址取偶</font></p>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">格式：EVEN</font></p>
</blockquote>

<h3 align="left"><font FACE="宋体" size="5" color="#FFFFFF">八、注释和标记符</font></h3>

<blockquote>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">1、注释</font></p>
  <blockquote>
    <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">1）COMMENT&nbsp; / &nbsp; 
    注释&nbsp;&nbsp; /</font></p>
    <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">2）；注释</font></p>
  </blockquote>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">2、标记符</font></p>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">1）续行---&amp;</font></p>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">例如：</font></p>
  <blockquote>
    <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">DATA&nbsp; DW&nbsp; 12，34，</font></p>
    <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">&amp;&nbsp; 56</font></p>
  </blockquote>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">2）语句间隔符---！</font></p>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">例如：</font></p>
  <blockquote>
    <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">MOV&nbsp; AX，@DATA ！MOV 
    &nbsp; DS，AX</font></p>
  </blockquote>
</blockquote>

<h3 align="left"><font FACE="宋体" size="5" color="#FFFFFF">九、运算符</font></h3>

<blockquote>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">1、分析运算符</font></p>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">1）取当前地址计数器的值---$</font></p>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">例如：</font></p>
  <blockquote>
    <blockquote>
      <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">VAL&nbsp; DW&nbsp; 12H，34H</font></p>
      <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">NUMER&nbsp; EQU&nbsp; $-VAL</font></p>
    </blockquote>
  </blockquote>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">2）取段地址值---SEG</font></p>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">例如：</font></p>
  <blockquote>
    <blockquote>
      <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">MOV&nbsp; AX，SEG&nbsp; VAL</font></p>
    </blockquote>
  </blockquote>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">3）取有效/偏移地址---OFFSET</font></p>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">例如：</font></p>
  <blockquote>
    <blockquote>
      <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">MOV&nbsp; BX，OFFSET &nbsp; 
      VAL</font></p>
      <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">LEA&nbsp; BX，VAL</font></p>
    </blockquote>
  </blockquote>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">4）取定义的变量个数---LENGTH</font></p>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">5）取定义的字节个数---SIZE</font></p>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">6）取定义的变量的类型的字节个数---TYPE</font></p>
  <div align="center"><center><table border="1" width="77%" bordercolor="#00FF00">
    <tr>
      <td width="16%" align="center"><big><big><font color="#FFFFFF">类型</font></big></big></td>
      <td width="16%" align="center"><big><big><font color="#FFFFFF">BYTE</font></big></big></td>
      <td width="17%" align="center"><big><big><font color="#FFFFFF">WORD</font></big></big></td>
      <td width="17%" align="center"><big><big><font color="#FFFFFF">DWORD</font></big></big></td>
      <td width="17%" align="center"><big><big><font color="#FFFFFF">NEAR</font></big></big></td>
      <td width="17%" align="center"><big><big><font color="#FFFFFF">FAR</font></big></big></td>
    </tr>
    <tr>
      <td width="16%" align="center"><big><big><font color="#FFFFFF">TYPE值</font></big></big></td>
      <td width="16%" align="center"><big><big><font color="#FFFFFF">1</font></big></big></td>
      <td width="17%" align="center"><big><big><font color="#FFFFFF">2</font></big></big></td>
      <td width="17%" align="center"><big><big><font color="#FFFFFF">4</font></big></big></td>
      <td width="17%" align="center"><big><big><font color="#FFFFFF">-1</font></big></big></td>
      <td width="17%" align="center"><big><big><font color="#FFFFFF">-2</font></big></big></td>
    </tr>
  </table>
  </center></div><p align="left"><font FACE="宋体" size="5" color="#FFFFFF">例如：</font></p>
  <blockquote>
    <blockquote>
      <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">VAL&nbsp; DW&nbsp; 5 &nbsp; 
      DUP（？）</font></p>
      <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">...</font></p>
      <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">MOV&nbsp; AX，LENGTH VAL</font></p>
      <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">MOV&nbsp; BX，SIZE&nbsp; VAL</font></p>
      <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">MOV&nbsp; CX，TYPE&nbsp; VAL</font></p>
    </blockquote>
  </blockquote>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">2、综合运算符</font></p>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">1）指定数据或地址类型---PTR</font></p>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">2）重新指定变量类型---THIS/LABEL</font></p>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">例如：</font></p>
  <blockquote>
    <blockquote>
      <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">VAL_B&nbsp; EQU&nbsp; THIS 
      &nbsp; BYTE</font></p>
      <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">VAL&nbsp; DW&nbsp; 1234H 
      &nbsp; </font></p>
      <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">...</font></p>
      <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">VAL_B&nbsp; LABEL&nbsp; BYTE</font></p>
      <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">VAL&nbsp; DW&nbsp; 1234H</font></p>
    </blockquote>
  </blockquote>
</blockquote>

<h3 align="left"><font FACE="宋体" size="5" color="#FFFFFF">十、程序结束</font></h3>

<blockquote>
  <blockquote>
    <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">END [标号]</font></p>
  </blockquote>
</blockquote>

<p align="left">　</p>

<h2 align="center"><font face="宋体" color="#FFFFFF"><big><big>§4.3 
典型结构程序设计</big></big></font></h2>

<h3 align="left"><font face="宋体" color="#FFFFFF"><big><big>一、几个常用的DOS功能调用</big></big></font></h3>

<blockquote>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">1、显示一个字符</font></p>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">入口：（AH）=2</font></p>
  <blockquote>
    <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">&nbsp;&nbsp; （DL）=显示字符的ASCII码。</font></p>
  </blockquote>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">执行：INT&nbsp; 21H</font></p>
  <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">例如：显示字母‘A’</font></p>
  <blockquote>
    <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">MOV&nbsp; AH，02</font></p>
    <p align="left"><font FACE="宋体" size="5" color="#FFFFFF">MOV&nbsp; DL，‘A’</font></p>