📄 c12_23.htm
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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title>练习题三 </title>
<script language="javascript">
function init(){
err1=err1div.style;
cor1=cor1div.style;
err2=err2div.style;
cor2=cor2div.style;
hint=hintdiv.style;
}
function show(obj){
obj.display='';
}
function hide(obj){
obj.display='none';
}
function judge1(){
var s1=document.form.T1.value;
if(s1=="32767"){
hide(err1);
show(cor1);
}else{
hide(cor1);
show(err1);
}
}
function judge2(){
var s2=document.form.T2.value;
if(s2=="-32768"){
hide(err2);
show(cor2);
}else{
hide(cor2);
show(err2);
}
}
</script>
</head>
<body bgcolor="#ccefcc" onLoad="init()">
<blockquote>
<p>首先, 若整数值范围是 -32768 至 32767。在执行下面的表达式之后, i
的结果是什么。<br>
</p>
<form name="form">
<div align="center"><center><table border="1" width="538">
<tr>
<td width="166">表达式</td>
<td width="188">结果</td>
<td width="166"> </td>
</tr>
<tr>
<td width="166">int i=32766;</td>
<td width="188">i==32766</td>
<td width="166"> </td>
</tr>
<tr>
<td width="166">i=i+1;</td>
<td width="188">i==<input type="text" name="T1" size="9"><input type="submit"
value="Enter" name="B1" onClick="judge1();return false"></td>
<td width="166"><div id="cor1div" style="display:'none'"><p><font color="#0000FF">正确!
做得很好!!</font></p>
</div><div id="err1div" style="display:'none'"><p><font color="#FF0000">错误!
请再试一遍!!</font></p>
</div></td>
</tr>
<tr>
<td width="166">i=i+1;</td>
<td width="188">i==<input type="text" name="T2" size="9"><input type="button"
value="Enter" name="B2" onClick="judge2()"></td>
<td width="166"><div id="cor2div" style="display:'none'"><p><font color="#0000FF">正确!
做得很好!!</font></p>
</div><div id="err2div" style="display:'none'"><p><font color="#FF0000">错误!
请再试一遍!!</font></p>
</div></td>
</tr>
</table>
</center></div>
</form>
<p><a href="javascript:show(hint)">提示:</a></p>
<div id="hintdiv" style="display:'none'"><p>在计算机中, 整数值的范围是从
-32768 至 32767。<br>
<br>
在计算机的内存中, 一个整型数占据两个字节。最大值是0111111111111111,
表示 32767。最小值 -32768 用 1000000000000000 表示。0111111111111110 表示
32766。0111111111111111 + 0000000000000001 = 1000000000000000。<br>
所以, 32766+1=32767, 而 32766+2=-32768。</p>
<div align="center"><center><table border="6" width="500" bgcolor="#CCFFFF"
bordercolor="#FF9933" cellspacing="0" cellpadding="0">
<tr>
<th width="100%" colspan="3" bgcolor="#FF9933">附:说明</th>
</tr>
<tr>
<td width="33%">类型</td>
<td width="33%">占内存空间</td>
<td width="34%">值的范围</td>
</tr>
<tr>
<td width="33%">int</td>
<td width="33%">2 bytes</td>
<td width="34%">-32768--32767</td>
</tr>
<tr>
<td width="33%">char</td>
<td width="33%">1 byte</td>
<td width="34%">0--255</td>
</tr>
<tr>
<td width="33%">unsign int</td>
<td width="33%">2 bytes</td>
<td width="34%">0--65535</td>
</tr>
<tr>
<td width="33%">long int</td>
<td width="33%">4 bytes</td>
<td width="34%">-4294967296--4294967295</td>
</tr>
<tr>
<td width="34%">short int</td>
<td width="33%">2 bytes</td>
<td width="33%">-32768--32767</td>
</tr>
<tr>
<td width="34%">float</td>
<td width="33%">4 bytes</td>
<td width="33%">单精度</td>
</tr>
<tr>
<td width="34%">double</td>
<td width="33%">8 bytes</td>
<td width="33%">双精度</td>
</tr>
</table>
</center></div></div>
</blockquote>
<p align="center"><a href="javascript:close()">关闭</a></p>
</body>
</html>
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