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<?xml version="1.0" encoding="utf-8"?>
<feed xmlns="http://www.w3.org/2005/Atom">
<title>KHUD's Blog</title>
<subtitle>Welcome!</subtitle>
<link href="http://8-u.github.io/atom.xml" rel="self"/>
<link href="http://8-u.github.io/"/>
<updated>2023-01-26T02:29:43.905Z</updated>
<id>http://8-u.github.io/</id>
<author>
<name>KHUD</name>
</author>
<generator uri="https://hexo.io/">Hexo</generator>
<entry>
<title>指针面试题</title>
<link href="http://8-u.github.io/posts/9896fd0f.html"/>
<id>http://8-u.github.io/posts/9896fd0f.html</id>
<published>2023-01-26T02:28:46.000Z</published>
<updated>2023-01-26T02:29:43.905Z</updated>
<content type="html"><![CDATA[<h1 id="【C语言面试题】"><a href="#【C语言面试题】" class="headerlink" title="【C语言面试题】"></a>【C语言面试题】</h1><h2 id="【知识点】"><a href="#【知识点】" class="headerlink" title="【知识点】"></a>【知识点】</h2><h3 id="【注意1】二维数组的初始化"><a href="#【注意1】二维数组的初始化" class="headerlink" title="【注意1】二维数组的初始化"></a>【注意1】二维数组的初始化</h3><p>int a[ 3 ] [ 2 ] = { {0,1},{2,3},{4,5} }; 内部应该为花括号。</p><p>注意与逗号表达式区分！！！！</p><p>同时二维数组的在内存中依然是按照顺序排放。</p><h3 id="【注意2】指针的初始化"><a href="#【注意2】指针的初始化" class="headerlink" title="【注意2】指针的初始化"></a>【注意2】指针的初始化</h3><p>1、指针指向一个数组 int* p = arr;</p><p>2、指针指向一串字符串 char* ptr = “abcdefg”;</p><p>3、用&符号</p><h3 id="【注意3】指针的运算"><a href="#【注意3】指针的运算" class="headerlink" title="【注意3】指针的运算"></a>【注意3】指针的运算</h3><p>指针的运算主要有三种：1、指针加减整数，跳过指针指向类型的个数</p><p> 2、指针减指针，得到的是两指针之间元素的个数，前提是两个指针指向同一块空间</p><p> 3、指针的关系运算 >, <, =</p><h3 id="【注意4】C语言运算符优先级"><a href="#【注意4】C语言运算符优先级" class="headerlink" title="【注意4】C语言运算符优先级"></a>【注意4】C语言运算符优先级</h3><p><img src="https://c2.im5i.com/2023/01/25/YTWRy.jpeg" alt="YTWRy.jpeg"></p><h2 id="【真题】"><a href="#【真题】" class="headerlink" title="【真题】"></a>【真题】</h2><h3 id="【真题1】"><a href="#【真题1】" class="headerlink" title="【真题1】"></a>【真题1】</h3><figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line"><span class="type">int</span> <span class="title function_">main</span><span class="params">()</span></span><br><span class="line">{</span><br><span class="line"> <span class="type">char</span>* c[] = { <span class="string">"ENTER"</span>,<span class="string">"NEW"</span>,<span class="string">"POINT"</span>,<span class="string">"FIRST"</span> };</span><br><span class="line"> <span class="type">char</span>** cp[] = { c + <span class="number">3</span>,c + <span class="number">2</span>,c + <span class="number">1</span>,c };</span><br><span class="line"> <span class="type">char</span>*** cpp = cp;</span><br><span class="line"> <span class="built_in">printf</span>(<span class="string">"%s\n"</span>, **++cpp);</span><br><span class="line"> <span class="built_in">printf</span>(<span class="string">"%s\n"</span>, *-- * ++cpp + <span class="number">3</span>);</span><br><span class="line"> <span class="built_in">printf</span>(<span class="string">"%s\n"</span>, *cpp[<span class="number">-2</span>] + <span class="number">3</span>);</span><br><span class="line"> <span class="built_in">printf</span>(<span class="string">"%s\n"</span>, cpp[<span class="number">-1</span>][<span class="number">-1</span>] + <span class="number">1</span>);</span><br><span class="line"> <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p><img src="https://c2.im5i.com/2023/01/25/YTX4O.jpeg" alt="YTX4O.jpeg"></p><h3 id="【真题2】"><a href="#【真题2】" class="headerlink" title="【真题2】"></a>【真题2】</h3><figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line"><span class="type">int</span> <span class="title function_">main</span><span class="params">()</span></span><br><span class="line">{</span><br><span class="line"><span class="type">int</span> a[<span class="number">3</span>][<span class="number">2</span>] = { (<span class="number">0</span>,<span class="number">1</span>),(<span class="number">2</span>,<span class="number">3</span>),(<span class="number">4</span>,<span class="number">5</span>) };</span><br><span class="line"> <span class="comment">//(0,1),(2,3),(4,5)都是逗号表达式，分别的值应该是1，3，5，所以这个二维数组中依次应该是a[0][0]=1,a[0][1]=3,a[1][0]=5,a[1][1]=0,a[2][0]=0,a[2][1]=0</span></span><br><span class="line"><span class="type">int</span>* p;</span><br><span class="line">p = a[<span class="number">0</span>];</span><br><span class="line"> <span class="comment">//p是一个整形指针，a[0]前面没有&和sizeof（），所以代表的是二维数组第一行的首元素地址，即指向a[0][0]=1</span></span><br><span class="line"><span class="built_in">printf</span>(<span class="string">"%d"</span>, p[<span class="number">0</span>]);</span><br><span class="line"> <span class="comment">//p[0]和*（p+0）是等同的，所以应该为1</span></span><br><span class="line"><span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">}</span><br><span class="line"></span><br></pre></td></tr></table></figure><p><img src="https://c2.im5i.com/2023/01/26/Y9SBl.png" alt="Y9SBl.png"></p><h3 id="【真题3】"><a href="#【真题3】" class="headerlink" title="【真题3】"></a>【真题3】</h3><figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line"><span class="type">int</span> <span class="title function_">main</span><span class="params">()</span></span><br><span class="line">{</span><br><span class="line"> <span class="type">int</span> a[<span class="number">5</span>][<span class="number">5</span>];</span><br><span class="line"> <span class="type">int</span>(*p)[<span class="number">4</span>];</span><br><span class="line"> p = a;</span><br><span class="line"> <span class="comment">//a前面既没有&也没有sizeof，所以a代表数组第一行的地址</span></span><br><span class="line"> <span class="built_in">printf</span>(<span class="string">"%p,%d\n"</span>, &p[<span class="number">4</span>][<span class="number">2</span>] - &a[<span class="number">4</span>][<span class="number">2</span>], &p[<span class="number">4</span>][<span class="number">2</span>] - &a[<span class="number">4</span>][<span class="number">2</span>]);</span><br><span class="line"> <span class="comment">//p[4][2]和 *(*(p+4)+2)等同，p是一个指向4元素数组的指针，+4代表跳过4个这样的数组，即p[4]再+2就是p[4][2]</span></span><br><span class="line"> <span class="comment">//指针-指针得到的是之间的元素个数，&p[4][2] - &a[4][2]中前者比后者小，得到-4，-4再以%p和%d的形式打印，%p是地址的形式，16进制的形式，%d就是-4</span></span><br><span class="line"> <span class="comment">//-4在计算机中是以2进制补码的形式存储，（32位系统）10000000000000000000000000000100（原码）</span></span><br><span class="line"> <span class="comment">// （32位系统）11111111111111111111111111111011（反码）</span></span><br><span class="line"> <span class="comment">// （32位系统）11111111111111111111111111111100（补码）——>转换成16进制形式FFFFFFFC</span></span><br><span class="line"> <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p><img src="https://c2.im5i.com/2023/01/26/Y9gY7.png" alt="Y9gY7.png"></p><h3 id="【真题4】"><a href="#【真题4】" class="headerlink" title="【真题4】"></a>【真题4】</h3><figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line"><span class="type">int</span> <span class="title function_">main</span><span class="params">()</span></span><br><span class="line">{</span><br><span class="line"> <span class="type">int</span> aa[<span class="number">2</span>][<span class="number">5</span>] = { <span class="number">1</span>,<span class="number">2</span>,<span class="number">3</span>,<span class="number">4</span>,<span class="number">5</span>,<span class="number">6</span>,<span class="number">7</span>,<span class="number">8</span>,<span class="number">9</span>,<span class="number">10</span> };</span><br><span class="line"> <span class="type">int</span>* ptr1 = (<span class="type">int</span>*)(&aa + <span class="number">1</span>);</span><br><span class="line"> <span class="comment">//很简单，就是指向数组尾部的地址</span></span><br><span class="line"> <span class="type">int</span>* ptr2 = (<span class="type">int</span>*)(*(aa + <span class="number">1</span>));</span><br><span class="line"> <span class="comment">//*（aa+1）代表aa[1],也就是拿到了第二行，第二行的名字即代表首元素地址，即aa[1][0]的地址，它本身就是一个整形指针，所以前面的强制类型转换完全是迷惑双眼的</span></span><br><span class="line"> <span class="built_in">printf</span>(<span class="string">"%d,%d"</span>, *(ptr1 - <span class="number">1</span>), *(ptr2 - <span class="number">1</span>));</span><br><span class="line"> <span class="comment">//ptr1[-1]是10，ptr2[-1]是5</span></span><br><span class="line"> <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p> <img src="https://c2.im5i.com/2023/01/26/Y9G72.png" alt="Y9G72.png"></p><h3 id="【真题5】"><a href="#【真题5】" class="headerlink" title="【真题5】"></a>【真题5】</h3><figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line"><span class="type">int</span> <span class="title function_">main</span><span class="params">()</span></span><br><span class="line">{</span><br><span class="line"> <span class="type">char</span>* a[] = { <span class="string">"work"</span> ,<span class="string">"at"</span>,<span class="string">"alibaba"</span> };</span><br><span class="line"> <span class="comment">//char* a[]是一个数组，数组中是char*指针，分别指向work，at，alibaba的首字符</span></span><br><span class="line"> <span class="type">char</span>** pa = a;</span><br><span class="line"> <span class="comment">//a是一个数组，并且前面没有&，sizeof，所以pa指向数组首元素的地址，即work首字符的地址</span></span><br><span class="line"> pa++;</span><br><span class="line"> <span class="comment">//pa是指向char*的指针，+1代表向后跳过一个char*，指向at的首字符的地址</span></span><br><span class="line"> <span class="built_in">printf</span>(<span class="string">"%s\n"</span>, *pa);</span><br><span class="line"> <span class="comment">//解引用得到at</span></span><br><span class="line"> <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p><img src="https://c2.im5i.com/2023/01/26/Y9PVP.png" alt="Y9PVP.png"></p>]]></content>
<summary type="html">指针一直是C语言的灵魂，无指针，不学C</summary>
</entry>
<entry>
<title>数据在内存中的存储</title>
<link href="http://8-u.github.io/posts/6601b08a.html"/>
<id>http://8-u.github.io/posts/6601b08a.html</id>
<published>2023-01-20T03:35:46.000Z</published>
<updated>2023-01-20T04:23:24.596Z</updated>
<content type="html"><![CDATA[<h1 id="【数据在内存中的存储】"><a href="#【数据在内存中的存储】" class="headerlink" title="【数据在内存中的存储】"></a>【数据在内存中的存储】</h1><h2 id="【内存是什么样子的？内存如何分配？】"><a href="#【内存是什么样子的？内存如何分配？】" class="headerlink" title="【内存是什么样子的？内存如何分配？】"></a>【内存是什么样子的？内存如何分配？】</h2><h3 id="【内存的样子】"><a href="#【内存的样子】" class="headerlink" title="【内存的样子】"></a>【内存的样子】</h3><p>内存可以想象成一个连续的物理空间。</p><p><img src="https://c2.im5i.com/2023/01/20/Y5CkD.png" alt="Y5CkD.png"></p><h3 id="【内存的分配】"><a href="#【内存的分配】" class="headerlink" title="【内存的分配】"></a>【内存的分配】</h3><h4 id="【总述】"><a href="#【总述】" class="headerlink" title="【总述】"></a>【总述】</h4><p>内存分配分为三种：静态、栈区、堆区。</p><p><img src="https://c2.im5i.com/2023/01/20/Y5hs2.png" alt="Y5hs2.png"></p><h4 id="【分别解释】"><a href="#【分别解释】" class="headerlink" title="【分别解释】"></a>【分别解释】</h4><p>（1）静态存储区：主要存放static静态变量、全局变量、常量。这些数据内存在编译的时候就已经为他们分配好了内存，生命周期是整个程序从运行到结束。</p><p>（2）栈区：存放局部变量。在执行函数的时候（包括main这样的函数），函数内的局部变量的存储单元会在栈上创建，函数执行完自动释放，生命周期是从该函数的开始执行到结束。</p><p><strong>栈区的使用习惯：先使用高地址，再使用低地址</strong>。</p><p>eg：</p><figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="type">int</span> <span class="title function_">main</span><span class="params">()</span></span><br><span class="line">{</span><br><span class="line"> <span class="type">int</span> i = <span class="number">3</span>;</span><br><span class="line"> <span class="type">int</span> arr[<span class="number">2</span>] = {<span class="number">1</span>,<span class="number">2</span>};</span><br><span class="line"> <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">}</span><br><span class="line"><span class="comment">//【注】：i和arr数组是局部变量，存放在栈区，而栈区使用习惯是先使用高地址，再使用低地址，而且一般的家庭计算机数据存储方式是小端存储，所以i和arr在内存上应该是这样：</span></span><br></pre></td></tr></table></figure><p><img src="https://c2.im5i.com/2023/01/20/Y5QC7.png" alt="Y5QC7.png"></p><p>（3）堆区：程序员自己申请一块任意大小的内存—也叫动态内存分配。这块内存会一直存在直到程序员释放掉。C语言中，用malloc or new动态地申请内存，用free or delete释放内存。良好习惯：若申请的动</p><p>态内存不再使用，要及时释放掉，否则会造成内存泄露。</p><h2 id="【C语言中有那些数据类型呢？】"><a href="#【C语言中有那些数据类型呢？】" class="headerlink" title="【C语言中有那些数据类型呢？】"></a>【C语言中有那些数据类型呢？】</h2><h3 id="【整形家族】"><a href="#【整形家族】" class="headerlink" title="【整形家族】"></a>【整形家族】</h3><p>（1）char: unsigned char 和 signed char(注：char虽然是字符类型，但是本质上以ASCII码，即数字存储) 占位1字节</p><p>（2）short: unsigned short int 和 signed short int 占位2字节</p><p>（3）int: unsigned int 和 signed int 占位4字节</p><p>（4）long: unsigned long int 和 signed long int 占位4字节</p><h3 id="【浮点数家族】"><a href="#【浮点数家族】" class="headerlink" title="【浮点数家族】"></a>【浮点数家族】</h3><p>（1）float 占位4字节</p><p>（2）double 占位8字节</p><h3 id="【构造类型（自定义类型）】"><a href="#【构造类型（自定义类型）】" class="headerlink" title="【构造类型（自定义类型）】"></a>【构造类型（自定义类型）】</h3><p>（1）结构体类型（struct）</p><p>（2）数组（分为一维数组，二维数组，指针数组…）</p><p>（3）联合体（union）</p><p>（4）枚举（enum）</p><h3 id="【指针类型】"><a href="#【指针类型】" class="headerlink" title="【指针类型】"></a>【指针类型】</h3><p>（1）一级指针</p><p>（2）二级指针</p><p>（3）数组指针</p><p>（4）函数指针</p><h3 id="【空类型】"><a href="#【空类型】" class="headerlink" title="【空类型】"></a>【空类型】</h3><h2 id="【数据在内存中的存储】-1"><a href="#【数据在内存中的存储】-1" class="headerlink" title="【数据在内存中的存储】"></a>【数据在内存中的存储】</h2><h3 id="【数据的存储，需要考虑两方面，一是整数以补码的形式存储，二是大小端存储】"><a href="#【数据的存储，需要考虑两方面，一是整数以补码的形式存储，二是大小端存储】" class="headerlink" title="【数据的存储，需要考虑两方面，一是整数以补码的形式存储，二是大小端存储】"></a>【数据的存储，需要考虑两方面，一是整数以补码的形式存储，二是大小端存储】</h3><h4 id="【补码的表示】"><a href="#【补码的表示】" class="headerlink" title="【补码的表示】"></a>【补码的表示】</h4><p>（1）正整数：原码、反码、补码相同</p><p>（2）负整数：以signed int a = -10为例</p><p>原码:10000000000000000000000000001010</p><p>反码:11111111111111111111111111110101</p><p>补码:11111111111111111111111111110110</p><h4 id="【大小端存储】"><a href="#【大小端存储】" class="headerlink" title="【大小端存储】"></a>【大小端存储】</h4><p><strong>数据的低位在低地址为小端存储。</strong></p><p><strong>数据的低位在高地址为大端存储。</strong></p><h5 id="【那么何为数据的低位和高位呢？】"><a href="#【那么何为数据的低位和高位呢？】" class="headerlink" title="【那么何为数据的低位和高位呢？】"></a>【那么何为数据的低位和高位呢？】</h5><p>二进制：10111100000（左边高位，右边低位），八进制，十六进制等同上，权值高的是数据的高位。</p><h5 id="【如何判断计算机大小端？】"><a href="#【如何判断计算机大小端？】" class="headerlink" title="【如何判断计算机大小端？】"></a>【如何判断计算机大小端？】</h5><figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line"><span class="type">int</span> <span class="title function_">main</span><span class="params">()</span></span><br><span class="line">{</span><br><span class="line"> <span class="type">int</span> a = <span class="number">1</span>;<span class="comment">//补码是00000000000000000000000000000001</span></span><br><span class="line"> <span class="type">char</span>* b = (<span class="type">char</span>*)&a;</span><br><span class="line"> <span class="keyword">if</span> (*b == <span class="number">0</span>)</span><br><span class="line"> {</span><br><span class="line"> <span class="built_in">printf</span>(<span class="string">"大端存储"</span>);</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">else</span></span><br><span class="line"> {</span><br><span class="line"> <span class="built_in">printf</span>(<span class="string">"小端存储"</span>);</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">}</span><br></pre></td></tr></table></figure><h3 id="【整形的存储】"><a href="#【整形的存储】" class="headerlink" title="【整形的存储】"></a>【整形的存储】</h3><p>以补码形式在内存中存储，存储时注意大小端的问题</p><h3 id="【浮点数的存储】"><a href="#【浮点数的存储】" class="headerlink" title="【浮点数的存储】"></a>【浮点数的存储】</h3><p><strong>【注】：浮点数在内存中存储仍有大小端的问题</strong></p><h4 id="【浮点数的表示】"><a href="#【浮点数的表示】" class="headerlink" title="【浮点数的表示】"></a>【浮点数的表示】</h4><p>根据国际标准IEEE（电气电子工程师学会）754，任意一个二进制浮点数V都可以表示为以下形式：</p><p>V = （-1）^ S * M * 2 ^ E</p><p>S：符号位，只能是0或者1，当S为0时，V是正数。当S为1时，V是负数。</p><p>M：有效数，位于1到2区间内</p><p>E：指数位</p><p>eg：</p><p><img src="https://c2.im5i.com/2023/01/20/Yuk5n.png" alt="Yuk5n.png"></p><h4 id="【浮点数的存储】-1"><a href="#【浮点数的存储】-1" class="headerlink" title="【浮点数的存储】"></a>【浮点数的存储】</h4><h5 id="【float类型】"><a href="#【float类型】" class="headerlink" title="【float类型】"></a>【float类型】</h5><p>IEEE754规定：对于32位的float类型，最高的一位是符号位S，接着8位是指数E，剩下的23位是有效数M。</p><p><img src="https://c2.im5i.com/2023/01/20/Y51Al.png" alt="Y51Al.png"></p><h5 id="【double类型】"><a href="#【double类型】" class="headerlink" title="【double类型】"></a>【double类型】</h5><p>IEEE754规定：对于64位的double类型，最高的一位是符号位S，接着11位是指数E，剩下的52位是有效数M。</p><p><img src="https://c2.im5i.com/2023/01/20/Y5wIP.png" alt="Y5wIP.png"></p><h5 id="【浮点数有高低地址吗？】"><a href="#【浮点数有高低地址吗？】" class="headerlink" title="【浮点数有高低地址吗？】"></a>【浮点数有高低地址吗？】</h5><p>当然！浮点数在计算机中存储也需要考虑大小端的问题，对于浮点数，右边是低地址，左边是高地址</p><h5 id="【S、M、E怎么存入呢？】"><a href="#【S、M、E怎么存入呢？】" class="headerlink" title="【S、M、E怎么存入呢？】"></a>【S、M、E怎么存入呢？】</h5><p>（1）S，就直接存在第一位即可，0/1</p><p>（2）M，它的范围是（1，2），所以存入为了节省一位有效位，只存储小数点后面的位数，如 M = 1.0101，那么在M中就只存0101，剩余的位数补0</p><p>（3）E，IEEE规定指数位E是无符号数，而用 V = （-1）^ S * M * 2 ^ E 来表示时，E是有符号数，可能是负数【eg，0.1 = (-1)^0 * 1.0 * 2^(-1)】，在8位指数位下，E ∈（-127，128），在11位指数位下，E ∈（-1023，1024）</p><p>1、float，指数位E是8位，对于无符号数来说，E ∈（0.255），所以要在原本的E的基础上加上127，使它转化成无符号数。</p><p>2、double，指数位E是11位，对于无符号数来说，E ∈（0.2047），所以要在原本的E的基础上加上1023，使它转化成无符号数。</p><h5 id="【S、M、E怎么取出呢？】"><a href="#【S、M、E怎么取出呢？】" class="headerlink" title="【S、M、E怎么取出呢？】"></a>【S、M、E怎么取出呢？】</h5><p>（1）S，就直接取出第一位即可，0/1</p><p>（2）M，取出小数点后面的位数后，再加上1.0即可，当E为全0时，加上0.0</p><p>（3）E，分为三种情况</p><p>1、E不是全0或全1</p><p>float，直接减127，double，直接减1023</p><p>2、E是全0</p><p>0-127后，得到E是-127，由 V = （-1）^ S * M * 2 ^ E 表达式可知，V非常小，所以IEEE规定，M取出后直接在前面加上0.0</p><p>0-1023后，同上</p><p>3、E是全1</p><p>float，11111111（十进制255）-127，得到E是128，由 V = （-1）^ S * M * 2 ^ E 表达式可知，V表示无穷大，无意义。</p><p>double，11111111111（十进制2047）-1023，得到E是1024，由 V = （-1）^ S * M * 2 ^ E 表达式可知，V表示无穷大，无意义。</p><h3 id="【构造类型（自定义类型）的存储-先以数组为例，其他待续…-】"><a href="#【构造类型（自定义类型）的存储-先以数组为例，其他待续…-】" class="headerlink" title="【构造类型（自定义类型）的存储(先以数组为例，其他待续…)】"></a>【构造类型（自定义类型）的存储(先以数组为例，其他待续…)】</h3><p>数组在地址中始终是数组的低位元素在低地址，高位元素在高地址。</p><p>其中一个元素的存储符合大小端的规则。（见1.2.2图）</p><h3 id="【指针类型的存储】"><a href="#【指针类型的存储】" class="headerlink" title="【指针类型的存储】"></a>【指针类型的存储】</h3><p>待续…</p>]]></content>
<summary type="html">数据在内存中的存储</summary>
</entry>
<entry>
<title>Markdown语法学习以及利用typora绘图</title>
<link href="http://8-u.github.io/posts/7207d55e.html"/>
<id>http://8-u.github.io/posts/7207d55e.html</id>
<published>2023-01-16T10:40:46.000Z</published>
<updated>2023-01-16T10:55:57.939Z</updated>
<content type="html"><![CDATA[<h1 id="Typora绘图"><a href="#Typora绘图" class="headerlink" title="Typora绘图"></a>Typora绘图</h1><h2 id="饼状图（Click-the-Photo）"><a href="#饼状图（Click-the-Photo）" class="headerlink" title="饼状图（Click the Photo）"></a>饼状图（Click the Photo）</h2><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">pie</span><br><span class="line">title 暗网占比</span><br><span class="line">"色情":452</span><br><span class="line">"毒品":1265</span><br><span class="line">"比特币":569</span><br></pre></td></tr></table></figure><h2 id="时序图（Click-the-Photo）"><a href="#时序图（Click-the-Photo）" class="headerlink" title="时序图（Click the Photo）"></a>时序图（Click the Photo）</h2><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"></span><br></pre></td></tr></table></figure>]]></content>
<summary type="html">Markdown语法学习以及利用typora绘图</summary>
</entry>
</feed>