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<span style="background-color: #CCFF99">第 7 章</span><span style="background-color: #CCFF99">
</span>><span style="background-color: #CCFF99"> 第 5 节 </span>><span style="background-color: #CCFF99">
7.5 </span><span style="background-color: #CCFF99">习题</span></p>
<hr color="#008000" size="1">
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">1.
<font LANG="ZH-CN">编写一个程序，它读入一个文件，并统计文件中的行数。</font></font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">2.
<font LANG="ZH-CN">设字符串</font>string="1 2 3 4 5 6 7 8 9"<font LANG="ZH-CN">，用字符串流</font>I/O<font LANG="ZH-CN">的方法编程逐个读取这个串的每一个数，直到读完为止，并在屏幕上输出。</font></font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">3.
<font LANG="ZH-CN">实现一个通讯录显示程序，通讯录的记录格式为：</font></font></p>
<font SIZE="3">
<blockquote>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"></font><font LANG="ZH-CN" size="2">姓名，单位，电话，住址，家庭电话</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2"><font LANG="ZH-CN">要求先建立</font>Person<font LANG="ZH-CN">类，然后按对象读入和输出。</font></font></p>
</blockquote>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">4.
<font LANG="ZH-CN">请写出下面程序的运行结果。</font></font></p>
<blockquote>
<blockquote>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">#include<iostream.h></font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">#include<fstream.h></font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">void
main( )</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">{ </font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">int
i;</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">double
x;</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">char
a[10],b[10];</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">ofstream
os1,os2("abc2.dat"); //os1<font LANG="ZH-CN">是个</font>ofstream<font LANG="ZH-CN">类的没有初始值的对象</font>(<font LANG="ZH-CN">没有打开文件</font>)</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">os1.open("abc1.dat");
//<font LANG="ZH-CN">对象</font>os1<font LANG="ZH-CN">调用成员函数</font>open(
)<font LANG="ZH-CN">以缺省方式打开一个文件</font></font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">os1<<"shang
hai 123"<<endl; //<font LANG="ZH-CN">向文件</font>abc1.dat<font LANG="ZH-CN">中写入一行数据</font></font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">os2<<99.12<<endl<<"jiao_tong"<<endl;
//<font LANG="ZH-CN">向文件</font>abc2.dat<font LANG="ZH-CN">中写入二行数据</font></font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">os1.close(
);</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">os2.close(
);</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">ifstream
is1;</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">is1.open("abc1.dat");</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">is1>>a>>b>>i;</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">cout<<a<<"
"<<b<<" "<<(i*2)<<endl;</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">is1.close(
);
//<font LANG="ZH-CN">关闭文件，但对象</font>is1<font LANG="ZH-CN">依然存在</font></font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">is1.open("abc2.dat");</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">is1>>x>>a;</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">cout<<x<<"
"<<a<<endl;</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">os1.close(
);</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">fstream
fs("abc1.dat",ios::in|ios::out); //<font LANG="ZH-CN">以既可读又可写的方式打开文件</font></font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">fs>>a>>b>>i;
//<font LANG="ZH-CN">读完后文件指针指向下一个</font></font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">cout<<"fs:
"<<a<<" "<<b<<"
"<<i<<endl;</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">fs<<"kkkkk
ppp "<<777<<endl; //<font LANG="ZH-CN">向文件</font>abc1.dat<font LANG="ZH-CN">中再写入一行数据</font></font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">fs.close(
);</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">fs.open("abc1.dat",ios::in);
//<font LANG="ZH-CN">以只读方式打开文件</font></font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">fs>>a>>b>>i;</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">cout<<"fs:
"<<a<<" "<<b<<"
"<<i<<endl;</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">fs>>a>>b>>i;</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">cout<<"fs:
"<<a<<" "<<b<<"
"<<i<<endl;</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">fs.close(
);</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">}</font></p>
</blockquote>
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