It may be a bit difficult to get started with C language learning, but after mastering the correct method, you will quickly master the basics and gradually master them. This guide will guide you step by step to learn the core concepts of C language, from basics to advanced topics.

Table of contents

1. Basics and data types of C language
2. User input
3. Abbreviation of conditional expressions
4. Switch statement
5. C language array
6. Nested loops
7. C language functions
8. Structure
9. pointer

Basics and data types of C language

The C program follows a standard structure and defines variables using multiple data types. The basic program structure is as follows:

 <code class="c">#include <stdio.h> int main() { printf("hello, world!"); return 0; }</stdio.h></code>

Core concept:

• Data type:
  • int : integer (e.g. int x = 10; ).
  • float and double : single-precision and double-precision floating point numbers (e.g. float pi = 3.14; ).
  • char : a single character or ASCII code (e.g., char letter = 'a'; ).
  • bool : Boolean value ( true or false , it must include the <stdbool.h></stdbool.h> header file).

 <code class="c">// 數(shù)據(jù)類型示例： int a = 40; // 整數(shù)(4字節(jié)) short int b = 32767; // 短整型(2字節(jié)，范圍：-32768到32767) unsigned int c = 4294967295; // 無符號(hào)整數(shù)(4字節(jié)，范圍：0到4294967295) float d = 9.81; // 單精度浮點(diǎn)數(shù)(4字節(jié)，精度6-7位，格式：%f) double e = 3.141592653589793; // 雙精度浮點(diǎn)數(shù)(8字節(jié)，精度15-16位，格式：%lf) bool f = true; // 布爾值(1字節(jié)，true/false，格式：%d，其中1=true，0=false) char g = 'e'; // 字符(1字節(jié)，可用于字符或數(shù)字) char h = 100; // 字符(1字節(jié)，格式：%d表示數(shù)字，%c表示ASCII碼，范圍：-128到127) char name[] = "example"; // 字符串// 變量聲明和初始化int age; // 聲明age = 5; // 初始化char language = 'c'; // 聲明和初始化// 顯示變量printf("你%d歲了", age); // 整數(shù)printf("你好%s", name); // 字符串printf("你現(xiàn)在正在學(xué)習(xí)%c", language); // 字符// 格式說明符：%d -> int, %s -> string, %c -> char, %f -> float, %.(numberofdecimals)f -> 帶指定小數(shù)位的浮點(diǎn)數(shù)</code>

• Operator:

 <code class="c">/* = 加法- = 減法* = 乘法/ = 除法% = 取模= 自增1 -- = 自減1 */ // 結(jié)果需要存儲(chǔ)在與結(jié)果類型匹配的變量中// 數(shù)據(jù)類型轉(zhuǎn)換： int x = 5; int y = 2; float z = 5/2; // 錯(cuò)誤結(jié)果，因?yàn)閤和y是整數(shù)float z = 5 / (float)2; // 正確方法// 單變量自增： int x = 4; x = 2; // x = 6 x -= 2; // x = 4 x *= 2; // x = 8 x /= 2; // x = 4</code>

User input

In VS Code, you need to switch from "Output" to "Terminal" window to run the program because the terminal receives user input.

 <code class="c">int age; char name[25]; // 用戶輸入整數(shù)： printf("你幾歲了？\n"); // 顯示提示信息scanf("%d", &age); // 指定數(shù)據(jù)類型和變量名printf("你%d歲了", age); // 用戶輸入字符串（字符數(shù)組）： printf("你的名字是？"); scanf("%s", name); printf("你好%s，你好嗎？", name); /* scanf() 不讀取空格，如果需要輸入姓名和姓氏，可以使用fgets函數(shù)：結(jié)構(gòu)： fgets(變量名, 大小, stdin) */ fgets(name, 25, stdin); // fgets 也包含結(jié)尾的'\n'</code>

C language is case sensitive If capitalization values ??are required, you can modify the user input to get the correct value. For example:

 <code class="c">#include <ctype.h> // 我們要求用戶輸入大寫F或大寫C char unit; printf("溫度是攝氏度(c)還是華氏度(f)？"); scanf(" %c", &unit); // 注意%c前的空格，用于去除前導(dǎo)空格// 修改用戶輸入： unit = toupper(unit); // 現(xiàn)在，即使用戶輸入小寫c或f，我們也保存大寫值到unit if(unit == 'C'){ printf("溫度目前是攝氏度。"); } else if (unit == 'F'){ printf("溫度目前是華氏度。"); } else{ printf("%c 不是正確的值", unit); }</ctype.h></code>

Conditional expression abbreviation

C language uses ternary operators to simplify if-else conditional statements:

 <code class="c">int max = (a > b) ? a : b;</code>

Equivalent to:

 <code class="c">if (a > b) { max = a; } else { max = b; }</code>

This is a simple and efficient way to write simple conditional logic.

Switch statement

The switch statement allows processing of multiple possible values ??of a variable:

 <code class="c">char grade = 'a'; // 聲明變量'grade'并初始化為'a' switch (grade) { // 開始switch語(yǔ)句檢查'grade'的值case 'a': // 如果'grade'是'a' printf("優(yōu)秀!\n"); // 打印"優(yōu)秀!" break; // 退出switch語(yǔ)句case 'b': // 如果'grade'是'b' printf("良好!\n"); // 打印"良好!" break; // 退出switch語(yǔ)句default: // 如果'grade'不是'a'或'b' printf("下次加油。\n"); // 打印"下次加油。" }</code>

Always include default case handling unexpected values.

C language array

An array is a collection of variables of the same type stored in memory in order. For example:

 <code class="c">int numbers[5] = {10, 20, 30, 40, 50};</code>

Core concept:

• Access elements: Use array index, starting from 0:

 <code class="c">printf("%d", numbers[0]); // 打印10</code>

• Two-dimensional array: similar to matrix or grid:

 <code class="c">int matrix[2][3] = { // 聲明一個(gè)2行3列的二維數(shù)組'matrix' {1, 2, 3}, // 初始化第一行{4, 5, 6} // 初始化第二行};</code>

• String array: Arrays can also store strings:

 <code class="c">// 聲明一個(gè)字符串?dāng)?shù)組'cars'，每個(gè)字符串最大長(zhǎng)度為10個(gè)字符char cars[][10] = {"bmw", "tesla", "toyota"};</code>

Arrays are widely used to process data lists, grids, or tables.

Nested loops

A nested loop is when one loop contains another loop, which is usually used to deal with grids or repetitive patterns:

 <code class="c">for (int i = 0; i </code>

This is great for handling multi-dimensional arrays or creating complex output.

C language functions

Functions allow code reuse. For example:

 <code class="c">void greet() { printf("hello, world!\n"); printf("歡迎學(xué)習(xí)C語(yǔ)言編程。\n"); printf("讓我們開始編碼吧!\n"); } int main() { greet(); return 0; }</code>

Functions can accept parameters to make them more flexible:

 <code class="c">void greet(char name[]) { printf("你好，%s!\n", name); } int main() { greet("Alice"); return 0; }</code>

Using functions helps keep code organized and reusable.

Structure

The structure ( struct ) combines the relevant variables under one name:

 <code class="c">// 定義一個(gè)名為'player'的結(jié)構(gòu)體，包含兩個(gè)成員struct player { char name[50]; // 字符數(shù)組'name'存儲(chǔ)玩家姓名(最多50個(gè)字符) int score; // 整數(shù)'score'存儲(chǔ)玩家分?jǐn)?shù)}; // 創(chuàng)建一個(gè)'player'結(jié)構(gòu)體的實(shí)例并初始化struct player player1 = {"Alice", 100}; // 初始化'player1'，姓名為"Alice"，分?jǐn)?shù)為100 // 打印玩家姓名和分?jǐn)?shù)printf("姓名：%s，分?jǐn)?shù)：%d", player1.name, player1.score); // 輸出：姓名：Alice，分?jǐn)?shù)：100</code>

Structures are often used to create complex data models, such as records or objects.

pointer

Pointers are variables that store memory addresses, which can achieve efficient data processing:

 <code class="c">int value = 42; // 聲明一個(gè)整數(shù)變量'value'并初始化為42 int *ptr = &value; // 聲明一個(gè)指向整數(shù)的指針變量'ptr'并將其初始化為'value'的地址printf("值：%d，地址：%p", *ptr, ptr); // 打印'ptr'指向的值和'ptr'存儲(chǔ)的地址</code>

It is crucial to target dynamic memory allocation and underlying operations in C language.

Learn C language and accumulate this practical information. Mastering these concepts will lay a solid foundation for your C programming. Take this guide as a reference and practice regularly and you will soon grow from a beginner to a C language expert. Have a happy programming!

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