2024-08-04 05:08:16 +02:00
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import{_ as s,c as i,o as a,a6 as n}from"./chunks/framework.CZKtKhAm.js";const l="/c/assets/1.CXNJqOOc.png",e="/c/assets/2.E0LS08Y5.png",t="/c/assets/3.6recRAvz.jpeg",p="/c/assets/4.DcyDw4rB.jpg",h="/c/assets/5.q20QOAIA.png",d="/c/assets/6.CmrWpBzQ.png",k="/c/assets/7.CocAjZjO.png",r="/c/assets/8.CHZSlb-7.png",c="/c/assets/9.RD2M_pYn.png",o="/c/assets/10.CmNKK_Ug.png",u="/c/assets/11.CbGZ55Dj.png",E="/c/assets/12.DpTBR420.png",b="/c/assets/13.XcPl7d9s.png",g="/c/assets/14.DL02VQMp.png",F="/c/assets/15.Dr67r_Ws.png",y="/c/assets/16.C5XiXNVN.png",m="/c/assets/17.DO8XxSV6.jpg",C="/c/assets/18.CUXrdefp.jpeg",B="/c/assets/19.uqLiL_yu.png",v="/c/assets/20.CkykpHY2.png",A="/c/assets/21.DV1YbrOP.png",D="/c/assets/22.AHNJT9TV.png",_="/c/assets/23.Bs-MOwx2.png",q="/c/assets/24.StzjmBz-.png",f="/c/assets/25.C0wVWaxD.png",x="/c/assets/26.LXJMAihe.png",P="/c/assets/27._UTCq3PD.png",O="/c/assets/28.BjQ5kBL-.png",T="/c/assets/29.COIOzcmT.png",N="/c/assets/30.Cu__mjav.png",M="/c/assets/31.BX_KzkHt.png",w="/c/assets/32.COt_QxSP.png",K=JSON.parse('{"title":"第一章：变量（⭐）","description":"","frontmatter":{},"headers":[],"relativePath":"notes/01_c-basic/02_xdx/index.md","filePath":"notes/01_c-basic/02_xdx/index.md","lastUpdated":1722740854000}'),I={name:"notes/01_c-basic/02_xdx/index.md"},U=n('<h1 id="第一章-变量-⭐" tabindex="-1">第一章：变量（⭐） <a class="header-anchor" href="#第一章-变量-⭐" aria-label="Permalink to "第一章：变量（⭐）""></a></h1><h2 id="_1-1-程序中变化的数据" tabindex="-1">1.1 程序中变化的数据 <a class="header-anchor" href="#_1-1-程序中变化的数据" aria-label="Permalink to "1.1 程序中变化的数据""></a></h2><ul><li>在生活中，我们使用最多的不是固定的数据，而是会变化的数据： <ul><li>① 购物车商品的<code>数量</code>、<code>价格</code>等。</li><li>② 一首歌<code>播放的时间</code>、<code>进度条</code>、<code>歌词的展示</code>等。</li><li>③ 微信聊天中<code>消息条数</code>、<code>时间</code>、<code>语音的长度</code>、<code>头像</code>、<code>名称</code>等。</li><li>④ 游戏中技能的<code>冷却时间</code>、<code>血量</code>、<code>蓝量</code>、<code>buff 时间</code>、<code>金币的数量</code>等。</li><li>……</li></ul></li></ul><ul><li>下图是一个<code>购物车</code>中<code>变化</code>的<code>数据</code>，即：</li></ul><p><img src="'+l+'" alt=""></p><ul><li>那么，在实际开发中，我们就会使用<code>变量</code>来<code>保存</code>和<code>操作</code>这些<code>变化</code>的<code>数据</code>。</li></ul><h2 id="_1-2-变量" tabindex="-1">1.2 变量 <a class="header-anchor" href="#_1-2-变量" aria-label="Permalink to "1.2 变量""></a></h2><ul><li>变量的定义：变量是程序中不可或缺的组成单位，最基本的存储单元。其实，变量就是一个存储数据的临时空间，可以向其中存储不同类型的数据，如：整数、小数、字符、字符串等，并且变量中的数据在程序运行的时候可以动态改变。</li></ul><div class="note custom-block github-alert"><p class="custom-block-title">NOTE</p><p></p><ul><li><code>变量</code>：用来<code>存储数据</code>的<code>容器</code>。</li><li><code>数据</code>：可以是一个用来计算的<code>数字</code>，如：上文购物车中的<code>价格</code>等；也可以是一句话中的<code>关键词</code>或<code>其它任意格式的数据</code>。</li><li>变量的<code>特别</code>之处就在于<code>它存放的数据是可以改变</code>的。</li></ul></div><ul><li>我们可以将<code>变量</code>想象为一个<code>容器</code>，盒子中<code>装的</code>就是我们想要的<code>数据</code>，并且我们需要<code>给</code>盒子<code>取</code>一个<code>特别的名称</code>；通过这个<code>特别的名称</code>，我们可以<code>给</code>盒子<code>添加数据</code>或<code>移除数据</code>，这个<code>特别
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2024-07-11 10:07:44 +02:00
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">int</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> main</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">() {</span></span>
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<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;"> // 声明一个整型变量，取名为 a</span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> int</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> a;</span></span>
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<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;"> // 给变量赋值</span></span>
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> a </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 10</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"a = </span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%d\\n</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, a);</span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> return</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 0</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span></span>
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br></div></div><ul><li>示例：初始化（声明变量的同时给其赋值）</li></ul><div class="language-c vp-adaptive-theme line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">c</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">#include</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;"> <stdio.h></span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">int</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> main</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">() {</span></span>
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<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;"> // 声明一个整型变量，取名为 b ，并直接赋值（初始化，实际开发中最为常用）</span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> int</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> b </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 200</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span></span>
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<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;"> // 修改变量 b 的值，将变量 a 的值赋值给变量 b</span></span>
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> b </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 300</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"b= </span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%d\\n</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, b);</span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> return</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 0</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span></span>
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br></div></div><ul><li>示例：同时声明多个变量并赋值</li></ul><div class="language-c vp-adaptive-theme line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">c</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">#include</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;"> <stdio.h></span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">int</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> main</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">() {</span></span>
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<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;"> // 同时声明多个整型的变量并赋值</span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> int</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> c1 </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 10</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, c2 </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 20</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, c3 </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 30</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"c1 = </span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%d\\n</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, c1);</span></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"c2 = </span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%d\\n</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, c2);</span></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"c3 = </span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%d\\n</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, c3);</span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> return</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 0</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span></span>
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2024-07-15 09:26:44 +02:00
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br></div></div><h2 id="_1-4-从计算机底层看变量" tabindex="-1">1.4 从计算机底层看变量 <a class="header-anchor" href="#_1-4-从计算机底层看变量" aria-label="Permalink to "1.4 从计算机底层看变量""></a></h2><h3 id="_1-4-1-内存条的内部结构" tabindex="-1">1.4.1 内存条的内部结构 <a class="header-anchor" href="#_1-4-1-内存条的内部结构" aria-label="Permalink to "1.4.1 内存条的内部结构""></a></h3><ul><li>如果只看内存条的外观，无非就是一些集成电路和颗粒而已，如下所示：</li></ul><p><img src="`+t+'" alt=""></p><ul><li>并且，我们只需要将内存条插入到计算机主板对应的内存条插槽上，就可以正常工作，如下所示：</li></ul><p><img src="'+p+'" alt=""></p><ul><li>在家用的台式机主板上，通常有 4 个插槽或 2 个插槽，例如：本人的计算机就支持 4 个插槽，如下所示：</li></ul><p><img src="'+h+'" alt=""></p><div class="note custom-block github-alert"><p class="custom-block-title">NOTE</p><p></p><ul><li>① 上图中的外形规格是 DIMM，所以我们通常也以 DIMM 也表示内存条。</li><li>② DIMM 是内存条的物理形式，安装在主板的内存插槽中。</li><li>③ 常见的 DIMM 类型包括 UDIMM（非缓冲 DIMM）、RDIMM（缓冲 DIMM）和 LRDIMM（负载减少DIMM）。</li></ul></div><ul><li>我们可以通过 <a href="https://www.cpuid.com/" target="_blank" rel="noreferrer">CPU-Z</a> 这个软件，查看 CPU 的一些指标信息，如下所示：</li></ul><p><img src="'+d+'" alt=""></p><div class="note custom-block github-alert"><p class="custom-block-title">NOTE</p><p></p><ul><li>① 通过 CPU-Z 表明本人的台式机是支持双通道的，<code>channel</code> 在<code>计算机</code>中可以<code>翻译</code>为<code>信道</code>或<code>通道</code>。</li><li>② 通道是内存控制器与内存模块之间的通信路径。</li><li>③ 多通道内存可以提高数据传输带宽。例如：双通道内存系统同时使用两个通道来传输数据，从而提高性能。</li><li>④ 现代主板通常支持双通道（Dual Channel）、四通道（Quad Channel）甚至八通道（Octa Channel）。</li></ul></div><ul><li>对于家用台式机而言，如果将内存条的插槽从左到右依次编号，如下所示：</li></ul><p><img src="'+k+'" alt=""></p><ul><li>其中，<code>槽1</code> 和 <code>槽2</code> 是一个通道，<code>槽3</code> 和 <code>槽4</code> 是一个通道；所以，通常是这么建议的： <ul><li>如果只有 1 根内存条，就插到 <code>槽2</code> 中。</li><li>如果有 2 根内存条，就分别插入到 <code>槽2</code> 和 <code>槽4</code> 中。</li><li>如果有 4 根内存条，就全插满即可。</li></ul></li></ul><div class="note custom-block github-alert"><p class="custom-block-title">NOTE</p><p></p><p>组成双通道配置的内存条需要遵循一些基本要求来确保它们能够正常以双通道模式运行：</p><ul><li>① <strong>相同容量</strong>：理想情况下，组成双通道的内存条应该具有相同的容量。这样可以确保它们在处理数据时的一致性和兼容性。</li><li>② <strong>匹配的速度规格</strong>：内存条应该具有相同的速度规格，即它们的频率（如：DDR4-2400、DDR4-3200等）应该相同。不同速度的内存条可以一起工作，但系统会以所有内<EFBFBD>
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<span class="line"><span>0000,0001,000000000001 代表 LOAD B, 1</span></span>
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<span class="line"><span>0001,0001,000000010000 代表 STORE B, 16</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br></div></div><ul><li>这样，直接使用<code>内存地址</code>来编写代码（机器语言）实现是太难阅读、修改和维护了；于是，我们就使用了汇编语言来编写代码，并通过编译器来将汇编语言翻译为机器语言，即：</li></ul><div class="language-txt vp-adaptive-theme line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">txt</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span>LOAD A, 16 -- 编译 --> 0000,0000,000000010000</span></span>
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<span class="line"><span>LOAD B, 1 -- 编译 --> 0000,0001,000000000001</span></span>
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<span class="line"><span>STORE B, 16 -- 编译 --> 0001,0001,000000010000</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br></div></div><ul><li>但是，这样的汇编语言还是面向机器的，编程时仍然需要记住和管理大量内存地址，不具备程序的移植性；于是，我们就是使用了高级语言来编写代码，并引入了变量的概念，即：</li></ul><div class="language-c vp-adaptive-theme line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">c</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">int</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> num </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 10</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br></div></div><ul><li><p>我们使用<code>变量名</code>来<code>关联</code>内存<code>地址</code>，这样我们在编写代码的时候，就可以不用直接操作内存地址，极大地提高了代码的可读性和开发效率。并且，当程序运行完毕之后，程序所占用的内存还会交还给操作系统，以便其它程序使用。</p></li><li><p>综上所述，高级语言编译器的作用就是：</p><ul><li>① 编写源代码时使用变量名。</li><li>② 程序在经过编译器的编译之后，所有变量名被替换为具体地址。</li><li>③ ……</li></ul></li><li><p>此时，我们就可以知道，<code>变量</code>就是内存中用于<code>存储数据</code>的<code>临时空间</code>，并且变量中的值是可以变化的。</p></li><li><p><code>内存</code>中空间的<code>最小单位</code>是<code>字节</code>（Bytes），即 8 个 0 或 1 ，如下所示：</p></li></ul><div class="language-txt vp-adaptive-theme line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">txt</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span>00011001 00100110 00100110 00100110 00100110 ...</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br></div></div><div class="note custom-block github-alert"><p class="custom-block-title">NOTE</p><p></p><p>计算机中存储单位的换算，如下所示：</p><ul><li>1 B = 8 bit。</li><li>1 KB = 1024 B。</li><li>1 MB = 1024 KB。</li><li>1 GB = 1024 MB。</li><li>1 TB = 1024 GB 。</li><li>……</li></ul></div><ul><li>在内存中，每一个字节都有一个编号，这个编号我们称之为地址。一个变量至少占用 1 个字节（1 个或多个字节），我们将变量的第一个字节所占用的地址（变量的首地址），就称之为该变量的地址。CPU 就可以通过变量地址找到某个变量的值，然后拿到具体的数据进行计算了。</li></ul><div class="note custom-block github-alert"><p class="custom-block-title">NOTE</p><p></p><p>变量就是保存程序运行过程中临时产生的值。</p></div><ul><li><p>其实，到这里还是有疑惑的？我们说过，一个变量至少会占用 1 个字节，如果一个变量占用了 4 个字节，而 CPU 只会通过变量的地址（首地址）获取数据，那么 CPU 是如何获取完整的数据的？答案就是通过<code>数据类型</code>，数据类型除了限制数据的种类，还限制了数据在内存中所占空间的大小，如上图所示：</p><ul><li>① 假设变量 <code>a</code> 的首地址是 <code>01</code> ，变量的数据类型是 <code>4</code> 个字节。</li><li>② 那么，CPU 就会依次，从 <code>01 ~ 04</code> 中获取数据。</li>
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<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">// num 变量名 -- 关联内存中的一块存储空间</span></span>
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<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;">// = 10 将 10 存储到 num 所代表的 4 个字节的存储空间中</span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">int</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> num </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 10</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br></div></div><h2 id="_1-6-变量的重要操作" tabindex="-1">1.6 变量的重要操作 <a class="header-anchor" href="#_1-6-变量的重要操作" aria-label="Permalink to "1.6 变量的重要操作""></a></h2><h3 id="_1-6-1-变量的输出" tabindex="-1">1.6.1 变量的输出 <a class="header-anchor" href="#_1-6-1-变量的输出" aria-label="Permalink to "1.6.1 变量的输出""></a></h3><ul><li>在计算机中，所谓的<code>输入</code>和<code>输出</code>都是以计算机（CPU 和内存）为主体而言的，即：</li></ul><div class="note custom-block github-alert"><p class="custom-block-title">NOTE</p><p></p><p>输入：从输入设备(键盘、鼠标、扫描仪)向计算机输入数据。</p><p>输出：从计算机向外部输出设备(显示器、打印机)输出数据。</p></div><p><img src="`+b+`" alt=""></p><ul><li>在 C 语言中，提供了 <code>printf()</code> 函数用于输出信息，其函数声明是：</li></ul><div class="language-c vp-adaptive-theme line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">c</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">int</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> (</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">const</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> char</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> *</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">__format</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, ...) {</span></span>
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2024-07-11 10:07:44 +02:00
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> ...</span></span>
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2024-07-15 09:26:44 +02:00
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br></div></div><ul><li><code>printf</code> 的标准含义是格式化输出文本，来源于 <code>print formatted（格式化打印）</code>的缩写，其语法规则，如下所示：</li></ul><p><img src="`+g+'" alt=""></p><div class="note custom-block github-alert"><p class="custom-block-title">NOTE</p><p></p><ul><li>格式化字符串：是使用双引号括起来的字符串，里面包含了普通的字符串和格式占位符。</li><li>格式占位符（格式声明符）：由 <code>%</code> 和<code>格式字符</code>组成，作用是将输出的数据转换为指定的格式后输出，这里的 <code>%d</code> 表示整数。</li><li>输出列表：是程序要输出的一些数据，可以是常量、变量或表达式，需要和格式占位符一一对应。</li></ul></div><ul><li><p>在计算机中，二进制、八进制、十进制以及十六进制的英文名称和缩写，如下所示：</p><ul><li>二进制（binary），缩写是 bin。</li><li>八进制（octal），缩写是 oct。</li><li>十进制（decimal），缩写是 dec。</li><li>十六进制（Hexadecimal），缩写是 hex。</li></ul></li><li><p>其实，我们也可以在 Windows 系统中的计算器中来看到，即：</p></li></ul><p><img src="'+F+`" alt=""></p><div class="important custom-block github-alert"><p class="custom-block-title">IMPORTANT</p><p></p><p>在生活中的 decimal 是小数的意思；但是，在计算机中，decimal 的完整含义是 decimal integer ，即十进制整数。</p></div><ul><li>示例：</li></ul><div class="language-c vp-adaptive-theme line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">c</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">#include</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;"> <stdio.h></span></span>
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2024-07-11 10:07:44 +02:00
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">int</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> main</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">() {</span></span>
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<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;"> // 声明变量并赋值</span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> int</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> num </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 18</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span></span>
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<span class="line"></span>
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<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;"> // 使用输出语句，将变量 num 的值输出，其中 %d 表示输出的是整数</span></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"我今年</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%d</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">岁</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">\\n</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, num);</span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> return</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 0</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span></span>
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br></div></div><h3 id="_1-6-2-计算变量的大小" tabindex="-1">1.6.2 计算变量的大小 <a class="header-anchor" href="#_1-6-2-计算变量的大小" aria-label="Permalink to "1.6.2 计算变量的大小""></a></h3><ul><li><p>我们可以使用 <code>sizeof</code>关键字（运算符）来计算变量或类型所占内存空间的大小。</p></li><li><p>示例：</p></li></ul><div class="language-c vp-adaptive-theme line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">c</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">#include</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;"> <stdio.h></span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">int</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> main</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">() {</span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> int</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> num </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 10</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span></span>
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<span class="line"></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"变量所占内存空间的大小：</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%zd</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">字节</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">\\n</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">sizeof</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(num));</span></span>
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<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;"> // 数据类型所占内存空间的大小</span></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"数据类型所占内存空间的大小：</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%zd</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">字节</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">\\n</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">sizeof</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">int</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">));</span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> return</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 0</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span></span>
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br></div></div><h3 id="_1-6-3-获取变量的地址" tabindex="-1">1.6.3 获取变量的地址 <a class="header-anchor" href="#_1-6-3-获取变量的地址" aria-label="Permalink to "1.6.3 获取变量的地址""></a></h3><ul><li><p>在 C 语言中，我们可以使用<code>取地址运算符 &</code> 来获取变量的地址。</p></li><li><p>示例：</p></li></ul><div class="language-c vp-adaptive-theme line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">c</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">#include</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;"> <stdio.h></span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">int</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> main</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">() {</span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> int</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> num </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 10</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"变量 num 的值是：</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%d\\n</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, num);</span></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"变量 num 的地址(指针)是：</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%#p\\n</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">&</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">num);</span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> return</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 0</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span></span>
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br></div></div><h3 id="_1-6-4-变量的输入" tabindex="-1">1.6.4 变量的输入 <a class="header-anchor" href="#_1-6-4-变量的输入" aria-label="Permalink to "1.6.4 变量的输入""></a></h3><ul><li>在 C 语言中，提供了 <code>scanf()</code> 函数用于从标准输入（通常是键盘）中读取数据并根据变量的地址赋值给变量（变量需要提前声明），其函数声明是：</li></ul><div class="language-c vp-adaptive-theme line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">c</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">int</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> scanf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">const</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> char</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> *</span><span style="--shiki-light:#E36209;--shiki-dark:#FFAB70;">__format</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, ...) {</span></span>
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2024-07-11 10:07:44 +02:00
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> ...</span></span>
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2024-07-15 09:26:44 +02:00
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br></div></div><ul><li>其语法规则，如下所示：</li></ul><p><img src="`+y+`" alt=""></p><div class="note custom-block github-alert"><p class="custom-block-title">NOTE</p><p></p><p><code>&age</code>、<code>&num</code> 中的 <code>&</code>是寻址操作符，<code>&age</code> 表示变量 <code>age</code> 在内存中的地址。</p></div><div class="caution custom-block github-alert"><p class="custom-block-title">CAUTION</p><p></p><ul><li><p>① scanf() 函数中的 <code>%d</code>，如果是连着写，即：<code>%d%d</code>，那么在输入数据的时候，数据之间不可以使用逗号<code>,</code>分隔，只能使用空白字符（空格、tab 键或回车键），即：<code>2空格3tab</code>或<code>2tab3回车</code>等。</p></li><li><p>② 如果是 <code>%d,%d</code>，则输入的时候需要加上逗号<code>,</code>，即：<code>2,3</code>。</p></li><li><p>③ 如果是 <code>%d %d</code>，则输入的时候需要加上空格，即：<code>2空格3</code>。</p></li></ul></div><ul><li>示例：计算圆的面积，半径由用户指定</li></ul><div class="language-c vp-adaptive-theme line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">c</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">#include</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;"> <stdio.h></span></span>
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<span class="line"></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">int</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> main</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">() {</span></span>
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<span class="line"></span>
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2024-07-30 10:30:13 +02:00
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<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;"> // 禁用 stdout 缓冲区</span></span>
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<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;"> // CLion debug 独有，后文不再提及，如果 debug 有问题，就添加如下代码</span></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> setbuf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(stdout, </span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">NULL</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);</span></span>
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> </span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> float</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> radius;</span></span>
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<span class="line"></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"请输入一个半径："</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);</span></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> scanf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%f</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">&</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">radius);</span></span>
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<span class="line"></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> double</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> area </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 3.1415926</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> *</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> radius </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">*</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> radius;</span></span>
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<span class="line"></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"半径是</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%f</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">的圆的面积是</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%.2lf</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, radius, area);</span></span>
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<span class="line"></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> return</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 0</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span></span>
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2024-07-30 10:30:13 +02:00
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br><span class="line-number">18</span><br><span class="line-number">19</span><br></div></div><ul><li>示例：输入一个整数值，求其绝对值</li></ul><div class="language-c vp-adaptive-theme line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">c</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">#include</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;"> <stdio.h></span></span>
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2024-07-11 10:07:44 +02:00
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<span class="line"></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">int</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> main</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">() {</span></span>
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<span class="line"></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> int</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> num;</span></span>
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<span class="line"></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"请输入一个整数："</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);</span></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> scanf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%d</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">&</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">num);</span></span>
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<span class="line"></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> int</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> absNum;</span></span>
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<span class="line"></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> if</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> (num </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"><</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 0</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">) {</span></span>
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> absNum </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> -</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">num;</span></span>
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> } </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">else</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> {</span></span>
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> absNum </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> num;</span></span>
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> }</span></span>
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<span class="line"></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%d</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">的绝对值是：</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%d</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, num, absNum);</span></span>
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<span class="line"></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> return</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 0</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span></span>
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br><span class="line-number">18</span><br><span class="line-number">19</span><br><span class="line-number">20</span><br><span class="line-number">21</span><br></div></div><ul><li>示例：输入多个变量的值，求其乘积</li></ul><div class="language-c vp-adaptive-theme line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">c</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">#include</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;"> <stdio.h></span></span>
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<span class="line"></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">int</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> main</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">() {</span></span>
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<span class="line"></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> int</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> a, b, c;</span></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"请输入整数 a 、b 和 c 的值："</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);</span></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> scanf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%d</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> %d</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> %d</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">&</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">a, </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">&</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">b, </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">&</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">c);</span></span>
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<span class="line"></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> int</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> result </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> a </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">*</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> b </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">*</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> c;</span></span>
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<span class="line"></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%d</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;"> × </span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%d</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;"> × </span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%d</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;"> = </span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%d</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, a, b, c, result);</span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> return</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 0</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span></span>
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2024-07-15 09:26:44 +02:00
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br></div></div><h2 id="_1-7-标识符" tabindex="-1">1.7 标识符 <a class="header-anchor" href="#_1-7-标识符" aria-label="Permalink to "1.7 标识符""></a></h2><h3 id="_1-7-1-概述" tabindex="-1">1.7.1 概述 <a class="header-anchor" href="#_1-7-1-概述" aria-label="Permalink to "1.7.1 概述""></a></h3><ul><li>在 C 语言中，变量、函数、数组名、结构体等要素命名的时候使用的字符序列，称为标识符。</li></ul><div class="note custom-block github-alert"><p class="custom-block-title">NOTE</p><p></p><p>在上世纪 60 - 70 年代的时候，因为国家贫穷，人民生活不富裕等原因，家长虽然会给孩子取名为：<code>张建国</code>、<code>李华强</code>等；但是，也会取小名为<code>二狗子</code>、<code>狗剩</code>等，目的是希望孩子能健康成长（养活），像 <code>张建国</code>、<code>李华强</code>、<code>二狗子</code>、<code>狗剩</code>都是名字（标识符），伴随人的一生。</p></div><h3 id="_1-7-2-标识符的命名规范" tabindex="-1">1.7.2 标识符的命名规范 <a class="header-anchor" href="#_1-7-2-标识符的命名规范" aria-label="Permalink to "1.7.2 标识符的命名规范""></a></h3><ul><li><p>强制规范：</p><ul><li>① 只能由<code>小写</code>或<code>大写英文字母</code>，<code>0-9</code> 或 <code>_</code> 组成。</li><li>② 不能以<code>数字</code>开头。</li><li>③ 不可以是<code>关键字</code>。</li><li>④ 标识符具有<code>长度</code>限制，不同编译器和平台会有所不同，一般限制在 63 个字符内。</li><li>⑤ 严格<code>区分大小写字母</code>，如：Hello、hello 是不同的标识符。</li></ul></li><li><p>建议规范：</p><ul><li>① 为了提高阅读性，使用有意义的单词，见名知意，如：sum，name，max，year 等。</li><li>② 使用下划线连接多个单词组成的标识符，如：max_classes_per_student 等。</li><li>③ 多个单词组成的标识符，除了使用下划线连接，也可以使用小驼峰命名法，除第一个单词外，后续单词的首字母大写，如： studentId、student_name 等。</li><li>④ 不要出现仅靠大小写区分不同的标识符，如：name、Name 容易混淆。</li><li>⑤ 系统内部使用了一些下划线开头的标识符，如：C99 标准添加的类型 <code>_Bool</code>，为防止冲突，建议开发者尽量避免使用下划线开头的标识符。</li></ul></li><li><p>示例：合法（不一定建议）的标识符</p></li></ul><div class="language-txt vp-adaptive-theme line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">txt</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span>a、BOOK_sun、MAX_SIZE、Mouse、student23、Football、FOOTBALL、max、_add、num_1、sum_of_numbers</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br></div></div><ul><li>示例：非法的标识符</li></ul><div class="language-txt vp-adaptive-theme line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">txt</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span>$zj、3sum、ab#cd<EFBFBD>
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2024-07-11 10:07:44 +02:00
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">int</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> main</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">() {</span></span>
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<span class="line"><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 1</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span></span>
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<span class="line"><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;"> 'A'</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span></span>
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<span class="line"><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 12.3</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span></span>
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<span class="line"><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;"> "你好"</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> return</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 0</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span></span>
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br></div></div><ul><li>示例：字面量常量</li></ul><div class="language-c vp-adaptive-theme line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">c</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">#include</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;"> <stdio.h></span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">int</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> main</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">() {</span></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"整数常量 =》</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%d\\n</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, </span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">1</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);</span></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"字符常量 =》</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%c\\n</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, </span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">'A'</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);</span></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"浮点数常量 =》</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%f\\n</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, </span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">12.3</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);</span></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"字符串常量 =》</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%s\\n</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, </span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"你好"</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);</span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> return</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 0</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span></span>
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br></div></div><h2 id="_2-3-使用-define-定义常量" tabindex="-1">2.3 使用 #define 定义常量 <a class="header-anchor" href="#_2-3-使用-define-定义常量" aria-label="Permalink to "2.3 使用 #define 定义常量""></a></h2><ul><li><code>#define</code> 来定义常量，也叫作宏定义，就是用一个标识符来表示一个常量值，如果在后面的代码中出现了该标识符，那么编译时就全部替换成指定的常量值，即用宏体替换所有宏名，简称<code>宏替换</code>。</li><li>格式是：</li></ul><div class="language-c vp-adaptive-theme line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">c</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">#define 常量名 常量值</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br></div></div><div class="caution custom-block github-alert"><p class="custom-block-title">CAUTION</p><p></p><ul><li>① 其实<code>宏定义</code>的常量的<code>执行时机</code>是在<code>预处理</code>阶段，将所有<code>宏常量</code>替换完毕，才会继续编译代码。</li><li>② 不要以 <code>;</code> 结尾，如果有 <code>;</code> ，分号也会成为常量值的一部分。</li><li>③ <code># define</code> 必须写在 <code>main</code> 函数的外面！！！</li><li>④ <code>常量名</code>习惯用<code>大写字母</code>表示，如果多个单词，使用 <code>_</code> 来分隔，以便和变量区分。</li></ul></div><ul><li>示例：</li></ul><div class="language-c vp-adaptive-theme line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">c</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">#include</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;"> <stdio.h></span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">#define</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> PI</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 3.1415926</span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">int</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> main</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">() {</span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> double</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> radius </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 2.5</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> double</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> area </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> PI </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">*</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> radius </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">*</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> radius;</span></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"半径为</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%lf</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">的圆的面积是</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%.2lf</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, radius, area);</span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> return</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 0</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span></span>
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br></div></div><h2 id="_2-4-const-关键字" tabindex="-1">2.4 const 关键字 <a class="header-anchor" href="#_2-4-const-关键字" aria-label="Permalink to "2.4 const 关键字""></a></h2><ul><li>C99 标准新增，这种方式跟定义一个变量是类似的；只不过，需要在变量的数据类型前加上 <code>const</code> 关键字。</li><li>和使用 <code>#define定义宏常量</code>相比，const 定义的常量有详细的数据类型，而且会在编译阶段进行安全检查，在运行时才完成替换，所以会更加安全和方便。</li><li>格式是：</li></ul><div class="language-c vp-adaptive-theme line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">c</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">const</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> 数据类型 常量名 </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> 常量值;</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br></div></div><ul><li>示例：</li></ul><div class="language-c vp-adaptive-theme line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">c</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">#include</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;"> <stdio.h></span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">const</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> int</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> PI </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 3.1415926</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">int</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> main</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">() {</span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> double</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> radius </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 2.5</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> double</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> area </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> PI </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">*</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> radius </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">*</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> radius;</span></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"半径为</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%lf</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">的圆的面积是</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%.2lf</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, radius, area);</span></span>
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<span class="line"></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> return</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 0</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span></span>
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br></div></div><h2 id="_2-5-枚举常量" tabindex="-1">2.5 枚举常量 <a class="header-anchor" href="#_2-5-枚举常量" aria-label="Permalink to "2.5 枚举常量""></a></h2><ul><li>格式：</li></ul><div class="language-c vp-adaptive-theme line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">c</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">enum</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> 枚举常量 {</span></span>
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> xxx </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 1</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span></span>
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> yyy;</span></span>
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> ...</span></span>
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br></div></div><div class="note custom-block github-alert"><p class="custom-block-title">NOTE</p><p></p><ul><li>① 默认情况下，枚举常量是从 0 开始递增的。</li><li>② 也可以在定义枚举常量的时候，自定义它们的值。</li></ul></div><ul><li>示例：</li></ul><div class="language-c vp-adaptive-theme line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">c</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">#include</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;"> <stdio.h></span></span>
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<span class="line"></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">enum</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> sex {</span></span>
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> MALE </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 1</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">,</span></span>
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> FEMALE </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 2</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">,</span></span>
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">};</span></span>
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<span class="line"></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">int</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> main</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">() {</span></span>
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<span class="line"></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%d\\n</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, MALE);</span></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%d\\n</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, FEMALE);</span></span>
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<span class="line"></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> return</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 0</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span></span>
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br></div></div><ul><li>示例：</li></ul><div class="language-c vp-adaptive-theme line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">c</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">#include</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;"> <stdio.h></span></span>
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<span class="line"></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">enum</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> Sex {</span></span>
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> MALE </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 1</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">,</span></span>
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> FEMALE </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 2</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">,</span></span>
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">};</span></span>
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<span class="line"></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">int</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> main</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">() {</span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> enum</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> Sex sex;</span></span>
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<span class="line"></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"请输入性别(1 表示男性, 2 表示女性)："</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">);</span></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> scanf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%d</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">&</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">sex);</span></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"您的性别是：</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%d\\n</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, sex);</span></span>
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<span class="line"></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> return</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 0</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span></span>
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2024-07-15 09:26:44 +02:00
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br></div></div><h2 id="_2-6-defind-定义常量-vs-const-定义常量" tabindex="-1">2.6 #defind 定义常量 VS const 定义常量 <a class="header-anchor" href="#_2-6-defind-定义常量-vs-const-定义常量" aria-label="Permalink to "2.6 #defind 定义常量 VS const 定义常量""></a></h2><ul><li>① 执行时机：<code>#define</code> 是预处理指令，在编译<code>之前</code>执行；<code>const</code> 是关键字，在编译<code>过程</code>中执行。</li><li>② 类型检查：<code>#define</code> 定义常量<code>不用指定类型</code>，<code>不进行类型检查</code>，只是简单地文本替换；<code>const</code> 定义常量<code>需要指定数据类型</code>，<code>会进行类型检查</code>，类型安全性更强。</li></ul><h1 id="第三章-二进制" tabindex="-1">第三章：二进制 <a class="header-anchor" href="#第三章-二进制" aria-label="Permalink to "第三章：二进制""></a></h1><h2 id="_3-1-概述" tabindex="-1">3.1 概述 <a class="header-anchor" href="#_3-1-概述" aria-label="Permalink to "3.1 概述""></a></h2><ul><li>计算机的底层只有<code>二进制</code>，即计算机中<code>运算</code>和<code>存储</code>的<code>所有数据</code>都需要转换为<code>二进制</code>，包括：数字、字符、图片、视频等。</li></ul><p><img src="`+m+'" alt=""></p><ul><li>之前，我们也提到现代的计算机（量子计算机除外）几乎都遵循<code>冯·诺依曼</code>体系结构，其理论要点如下： <ul><li>① <strong>存储程序</strong>：<code>程序指令</code>和<code>数据</code>都存储在计算机的内存中，这使得程序可以在运行时修改。</li><li>② <strong>二进制逻辑</strong>：所有数据和指令都以<code>二进制</code>形式表示。</li><li>③ <strong>顺序执行</strong>：指令按照它们在内存中的顺序执行，但可以有条件地改变执行顺序。</li><li>④ <strong>五大部件</strong>：计算机由<code>运算器</code>、<code>控制器</code>、<code>存储器</code>、<code>输入设备</code>和<code>输出设备</code>组成。</li><li>⑤ <strong>指令结构</strong>：指令由操作码和地址码组成，操作码指示要执行的操作，地址码指示操作数的位置。</li><li>⑥ <strong>中心化控制</strong>：计算机的控制单元（CPU）负责解释和执行指令，控制数据流。</li></ul></li><li>所以，再次论证了为什么计算机只能识别二进制。</li></ul><h2 id="_3-2-进制" tabindex="-1">3.2 进制 <a class="header-anchor" href="#_3-2-进制" aria-label="Permalink to "3.2 进制""></a></h2><h3 id="_3-2-1-常见的进制" tabindex="-1">3.2.1 常见的进制 <a class="header-anchor" href="#_3-2-1-常见的进制" aria-label="Permalink to "3.2.1 常见的进制""></a></h3><ul><li>在生活中，我们最为常用的进制就是<code>十进制</code>，其规则是<code>满 10 进 1</code> ，即：</li></ul><p><img src="'+C+`" alt=""></p><ul><li>在计算机中，常见的进制有<code>二进制</code>、<code>八进制</code>和<code>十六进制</code>，即： <ul><li>二进制：只能 0 和 1 ，满 2 进 1 。</li><li>八进制：0 ~ 7 ，满 8 进 1 。</li><li>十六进制：
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2024-07-11 10:07:44 +02:00
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">int</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> main</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">() {</span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> int</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> num1 </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> 0b</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">10100110</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;"> // 二进制</span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> int</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> num2 </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> 0</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">717563</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;"> // 八进制</span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> int</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> num3 </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 1000</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;"> // 十进制</span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> int</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> num4 </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> 0x</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">af72</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;"> // 十六进制</span></span>
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<span class="line"></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"num1 = </span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%d\\n</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, num1);</span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;"> // num1 = 166</span></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"num2 = </span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%d\\n</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, num2);</span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;"> // num2 = 237427</span></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"num3 = </span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%d\\n</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, num3);</span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;"> // num3 = 1000</span></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"num4 = </span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%d\\n</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, num4);</span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;"> // num4 = 44914</span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> return</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 0</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span></span>
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br></div></div><h3 id="_3-2-3-输出格式" tabindex="-1">3.2.3 输出格式 <a class="header-anchor" href="#_3-2-3-输出格式" aria-label="Permalink to "3.2.3 输出格式""></a></h3><ul><li>在 C 语言中，可以使用不同的<code>格式占位符</code>来<code>输出</code>不同<code>进制</code>的整数，如下所示： <ul><li><code>%d</code>：十进制整数。</li><li><code>%o</code> ：八进制整数。</li><li><code>%x</code>：十六进制整数。</li><li><code>%#o</code> ：显示前缀 <code>0</code> 的八进制整数。</li><li><code>%#x</code> ：显示前缀 <code>0x</code> 的十六进制整数。</li><li><code>%#X</code> ：显示前缀 <code>0X</code> 的十六进制整数。</li></ul></li></ul><div class="caution custom-block github-alert"><p class="custom-block-title">CAUTION</p><p></p><p>C 语言中没有输出二进制数的格式占位符！！！</p></div><ul><li>示例：</li></ul><div class="language-c vp-adaptive-theme line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">c</span><pre class="shiki shiki-themes github-light github-dark vp-code" tabindex="0"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">#include</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;"> <stdio.h></span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">int</span><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> main</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">() {</span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> int</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> num </span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 100</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span></span>
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<span class="line"></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%d</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;"> 的十进制整数： </span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%d\\n</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, num, num);</span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;"> // 100 的十进制整数： 100</span></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%d</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;"> 的八进制整数： </span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%o\\n</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, num, num);</span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;"> // 100 的八进制整数： 144</span></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%d</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;"> 的十六进制整数： </span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%x\\n</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, num, num);</span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;"> // 100 的十六进制整数： 64</span></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%d</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;"> 的八进制（前缀）整数： </span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%#o\\n</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, num, num);</span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;"> // 100 的八进制（前缀）整数： 0144</span></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%d</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;"> 的十六进制（前缀）整数： </span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%#x\\n</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, num, num);</span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;"> // 100 的十六进制（前缀）整数： 0x64</span></span>
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<span class="line"><span style="--shiki-light:#6F42C1;--shiki-dark:#B392F0;"> printf</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%d</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;"> 的十六进制（前缀）整数： </span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">%#X\\n</span><span style="--shiki-light:#032F62;--shiki-dark:#9ECBFF;">"</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">, num, num);</span><span style="--shiki-light:#6A737D;--shiki-dark:#6A737D;"> // 100 的十六进制（前缀）整数： 0X64</span></span>
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<span class="line"></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;"> return</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;"> 0</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">;</span></span>
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2024-08-04 05:08:16 +02:00
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br></div></div><h2 id="_3-3-进制的运算规则" tabindex="-1">3.3 进制的运算规则 <a class="header-anchor" href="#_3-3-进制的运算规则" aria-label="Permalink to "3.3 进制的运算规则""></a></h2><ul><li><code>十进制</code>的运算规则，如下所示： <ul><li>逢<code>十</code>进<code>一</code>（针对加法而言）。</li><li>借<code>一</code>当<code>十</code>（针对减法而言）。</li></ul></li><li><code>二进制</code>的运算规则，如下所示： <ul><li>逢<code>二</code>进<code>一</code>（针对加法而言）。</li><li>借<code>一</code>当<code>二</code>（针对减法而言）。</li></ul></li><li><code>八进制</code>的运算规则，如下所示： <ul><li>逢<code>八</code>进<code>一</code>（针对加法而言）。</li><li>借<code>一</code>当<code>八</code>（针对减法而言）。</li></ul></li><li><code>十六进制</code>的运算规则，如下所示： <ul><li>逢<code>十六</code>进<code>一</code>（针对加法而言）。</li><li>借<code>一</code>当<code>十六</code>（针对减法而言）。</li></ul></li></ul><h2 id="_3-4-进制的转换" tabindex="-1">3.4 进制的转换 <a class="header-anchor" href="#_3-4-进制的转换" aria-label="Permalink to "3.4 进制的转换""></a></h2><h3 id="_3-4-1-概述" tabindex="-1">3.4.1 概述 <a class="header-anchor" href="#_3-4-1-概述" aria-label="Permalink to "3.4.1 概述""></a></h3><ul><li>不同进制的转换，如下所示：</li></ul><p><img src="`+B+'" alt=""></p><ul><li>在计算机中，数据是从右往左的方式排列的；其中，最右边的是低位，最左边的是高位，即：</li></ul><p><img src="'+v+'" alt=""></p><h3 id="_3-4-2-二进制和十进制的转换" tabindex="-1">3.4.2 二进制和十进制的转换 <a class="header-anchor" href="#_3-4-2-二进制和十进制的转换" aria-label="Permalink to "3.4.2 二进制和十进制的转换""></a></h3><h4 id="_3-4-2-1-二进制转换为十进制" tabindex="-1">3.4.2.1 二进制转换为十进制 <a class="header-anchor" href="#_3-4-2-1-二进制转换为十进制" aria-label="Permalink to "3.4.2.1 二进制转换为十进制""></a></h4><ul><li>规则：从最低位开始，将每个位上的数提取出来，乘以 2 的 （位数 - 1 ）次方，然后求和。</li></ul><div class="note custom-block github-alert"><p class="custom-block-title">NOTE</p><p></p><ul><li>① 在学术界，将这种计算规则，称为<code>位权相加法</code>。</li><li>② <code>八进制转换为十进制</code>、<code>十六进制转换为十进制</code>和<code>二进制转换为十进制</code>的算法相同！！！</li></ul></div><ul><li>示例：十进制转十进制</li></ul><p><img src="'+A+'" alt=""></p><ul><li>示例：二进制转十进制</li></ul><p><img src="'+D+'" alt=""></p><h4 id="_3-4-2-2-十进制转换二进制" tabindex="-1">3.4.2.2 十进制转换二进制 <a class="header-anchor" href="#_3-4-2-2-十进制转换二进制" aria-label="Permalink to "3.4.2.2 十进制转换二进制""></a></h4><ul><li>规则：将该数不断除以 2 ，直到商为 0 为止，然后将每步得到的余数倒过来，就是对应的二进制。</li></ul><div class="note custom-block github-alert"><p class="custom-block-title"
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