2024-08-22 08:36:19 +02:00
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import{_ as s,c as i,o as a,a6 as n}from"./chunks/framework.CZRoMP2i.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",d="/c/assets/5.q20QOAIA.png",h="/c/assets/6.CmrWpBzQ.png",c="/c/assets/7.CocAjZjO.png",k="/c/assets/8.CHZSlb-7.png",r="/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",g="/c/assets/13.XcPl7d9s.png",b="/c/assets/14.DL02VQMp.png",y="/c/assets/15.Dr67r_Ws.png",F="/c/assets/16.C5XiXNVN.png",m="/c/assets/17.DO8XxSV6.jpg",C="/c/assets/18.CUXrdefp.jpeg",v="/c/assets/19.BHR3Faxy.svg",B="/c/assets/20.BPvPBGLi.svg",A="/c/assets/21.96eXHKhR.svg",_="/c/assets/22.DU0JSGBx.svg",D="/c/assets/23.DjDYOeB4.svg",q="/c/assets/24.CSyqvmqg.svg",f="/c/assets/25.uqLiL_yu.png",x="/c/assets/26.CVy9jq-k.svg",P="/c/assets/27.D0s35-Np.svg",T="/c/assets/28.CGctd5l_.svg",O="/c/assets/29.DQIGB6FY.svg",N="/c/assets/30.DBiJDp82.svg",z="/c/assets/31.r0a7UWIb.svg",M="/c/assets/32.-KoNS5D_.svg",w="/c/assets/33.9LAsi3gH.svg",I="/c/assets/34.CbxjdJlI.svg",U="/c/assets/35.DouEaZ2q.svg",R="/c/assets/36.BAASpiz6.svg",S="/c/assets/37.CSLcq3FJ.svg",L="/c/assets/38.8wVUSUxs.svg",X="/c/assets/39.B8T792CZ.svg",j="/c/assets/40.D7XSVA_S.svg",V="/c/assets/41.BeI_-jpB.svg",as=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":1724308541000}'),G={name:"notes/01_c-basic/02_xdx/index.md"},J=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="" loading="lazy"></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><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:#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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<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-浅谈变量周边概念" tabindex="-1">1.4 浅谈变量周边概念 <a class="header-anchor" href="#_1-4-浅谈变量周边概念" aria-label="Permalink to "1.4 浅谈变量周边概念""></a></h2><h3 id="_1-4-1-数据类型" tabindex="-1">1.4.1 数据类型 <a class="header-anchor" href="#_1-4-1-数据类型" aria-label="Permalink to "1.4.1 数据类型""></a></h3><ul><li>数据是放在内存中的，变量是给这块内存起的名字，有了变量就可以找到并使用这份数据。但是，该如何使用？</li><li>我们知道，对于数字、文字、符号、图形、音频、视频等数据都是以二进制的形式被加载进内存中，进而被计算机中的 CPU 所识别，它们本质上没有任何区别。那么，对于 <code>00010000</code> 这个二进制数字，我们是理解为数字 16 ？还是理解为图像中的某个像素的颜色？如果没有特别指明，我们并不清楚。</li><li>换言之，内存中的数据有多种解释方式；那么，我们在存储之前就必须明确指定，如： <code>int num = 10;</code> 中的 <code>int</code> 就是数据类型，用来限定 <code>num</code> （内存中的某个区域）中存储的是整数，而不是图像中某个像素的颜色。</li></ul><div class="note custom-block github-alert"><p class="custom-block-title">NOTE</p><p></p><p>总结：</p><ul><li>① 数据类型用来说明数据的类型，确定了数据的解释方式，让计算机和程序员不会产生歧义。</li><li>② C 语言中很多基本的数据类型，如：char、short、int、long 等；如果需要，也可以组成更加复杂的数据类型（后续讲解）。</li></ul></div><h3 id="_1-4-2-连续定义多个变量" tabindex="-1">1.4.2 连续定义多个变量 <a class="header-anchor" href="#_1-4-2-连续定义多个变量" aria-label="Permalink to "1.4.2 连续定义多个变量""></a></h3><ul><li>为了让程序的书写更加简洁，C 语言支持多个变量的连续定义，如下所示：</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;"> a,b,c;</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br></div></div><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;">float</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> m</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">3.14</span><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;">,n</span><span style="--shiki-light:#D73A49;--shiki-dark:#F97583;">=</span><span style="--shiki-light:#005CC5;--shiki-dark:#79B8FF;">4.14</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>
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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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2024-08-22 08:36:19 +02:00
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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="_1-7-变量的重要操作" tabindex="-1">1.7 变量的重要操作 <a class="header-anchor" href="#_1-7-变量的重要操作" aria-label="Permalink to "1.7 变量的重要操作""></a></h2><h3 id="_1-7-1-变量的输出" tabindex="-1">1.7.1 变量的输出 <a class="header-anchor" href="#_1-7-1-变量的输出" aria-label="Permalink to "1.7.1 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="`+g+`" alt="" loading="lazy"></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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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#E1E4E8;"> ...</span></span>
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2024-08-15 05:48:49 +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="`+b+'" alt="" loading="lazy"></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="'+y+`" alt="" loading="lazy"></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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<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="_1-7-2-计算变量的大小" tabindex="-1">1.7.2 计算变量的大小 <a class="header-anchor" href="#_1-7-2-计算变量的大小" aria-label="Permalink to "1.7.2 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 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="_1-7-3-获取变量的地址" tabindex="-1">1.7.3 获取变量的地址 <a class="header-anchor" href="#_1-7-3-获取变量的地址" aria-label="Permalink to "1.7.3 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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2024-08-22 08:36:19 +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></div></div><h3 id="_1-7-4-变量的输入" tabindex="-1">1.7.4 变量的输入 <a class="header-anchor" href="#_1-7-4-变量的输入" aria-label="Permalink to "1.7.4 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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2024-08-15 05:48:49 +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="`+F+`" alt="" loading="lazy"></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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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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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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2024-07-11 10:07:44 +02:00
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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 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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2024-08-22 08:36:19 +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="_1-8-标识符" tabindex="-1">1.8 标识符 <a class="header-anchor" href="#_1-8-标识符" aria-label="Permalink to "1.8 标识符""></a></h2><h3 id="_1-8-1-概述" tabindex="-1">1.8.1 概述 <a class="header-anchor" href="#_1-8-1-概述" aria-label="Permalink to "1.8.1 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="_1-8-2-标识符的命名规范" tabindex="-1">1.8.2 标识符的命名规范 <a class="header-anchor" href="#_1-8-2-标识符的命名规范" aria-label="Permalink to "1.8.2 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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2024-08-19 09:41:14 +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-进制" tabindex="-1">第三章：进制 <a class="header-anchor" href="#第三章-进制" aria-label="Permalink to "第三章：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="" loading="lazy"></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="" loading="lazy"></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><
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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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2024-08-22 08:36:19 +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><h3 id="_3-3-1-概述" tabindex="-1">3.3.1 概述 <a class="header-anchor" href="#_3-3-1-概述" aria-label="Permalink to "3.3.1 概述""></a></h3><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><h3 id="_3-3-2-二进制的运算" tabindex="-1">3.3.2 二进制的运算 <a class="header-anchor" href="#_3-3-2-二进制的运算" aria-label="Permalink to "3.3.2 二进制的运算""></a></h3><ul><li>二进制的加法：<code>1 + 0 = 1</code> 、<code>1 + 1 = 10</code>、<code>11 + 10 = 101</code>、<code>111 + 111 = 1110</code>。</li></ul><p><img src="`+v+'" alt="" loading="lazy"></p><ul><li>二进制的减法：<code>1 - 0 = 1</code> 、<code>10 - 1 = 1</code>、<code>101 - 11 = 10</code>、<code>1100 - 111 = 101</code> 。</li></ul><p><img src="'+B+'" alt="" loading="lazy"></p><h3 id="_3-3-3-八进制的运算" tabindex="-1">3.3.3 八进制的运算 <a class="header-anchor" href="#_3-3-3-八进制的运算" aria-label="Permalink to "3.3.3 八进制的运算""></a></h3><ul><li>八进制的加法：<code>3 + 4 = 7</code> 、<code>5 + 6 = 13</code>、<code>75 + 42 = 137</code>、<code>2427 + 567 = 3216</code>。</li></ul><p><img src="'+A+'" alt="" loading="lazy"></p><ul><li>八进制的减法：<code>6 - 4 = 2</code> 、<code>52 - 27 = 33</code>、<code>307 - 141 = 146</code>、<code>7430 - 1451 = 5757</code> 。</li></ul><p><img src="'+_+'" alt="" loading="lazy"></p><h3 id="_3-3-4-十六进制的运算" tabindex="-1">3.3.4 十六进制的运算 <a class="header-anchor" href="#_3-3-4-十六进制的运算" aria-label="Permalink to "3.3.4 十六进制的运算""></a></h3><ul><li>十六进制的加法：<code>6 + 7 = D</code> 、<code>18 + BA = D2</code>、<code>595 + 792 = D27</code>、<code>2F87 + F8A = 3F11</code>。</li></ul><p><img src="'+D+'" alt="" loading="lazy"></p><ul><li>十六进制的减法：<code>D - 3 = A</code> 、<code>52 - 2F = 23</code>、<code>E07 - 141 = CC6</code>、<code>7CA0 - 1CB1 = 5FEF</code> 。</li></ul><p><img src="'+q+'" alt="" loading="lazy"></p><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=
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