C language starts from 0

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

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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="language-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="language-c">// 数据类型示例： int a = 40; // 整数(4字节) short int b = 32767; // 短整型(2字节，范围：-32768到32767) unsigned int c = 4294967295; // 无符号整数(4字节，范围：0到4294967295) float d = 9.81; // 单精度浮点数(4字节，精度6-7位，格式：%f) double e = 3.141592653589793; // 双精度浮点数(8字节，精度15-16位，格式：%lf) bool f = true; // 布尔值(1字节，true/false，格式：%d，其中1=true，0=false) char g = 'e'; // 字符(1字节，可用于字符或数字) char h = 100; // 字符(1字节，格式：%d表示数字，%c表示ASCII码，范围：-128到127) char name[] = "example"; // 字符串// 变量声明和初始化int age; // 声明age = 5; // 初始化char language = 'c'; // 声明和初始化// 显示变量printf("你%d岁了", age); // 整数printf("你好%s", name); // 字符串printf("你现在正在学习%c", language); // 字符// 格式说明符：%d -> int, %s -> string, %c -> char, %f -> float, %.(numberofdecimals)f -> 带指定小数位的浮点数</code>

• Operator:

 <code class="language-c">/* = 加法- = 减法* = 乘法/ = 除法% = 取模= 自增1 -- = 自减1 */ // 结果需要存储在与结果类型匹配的变量中// 数据类型转换： int x = 5; int y = 2; float z = 5/2; // 错误结果，因为x和y是整数float z = 5 / (float)2; // 正确方法// 单变量自增： int x = 4; x = 2; // x = 6 x -= 2; // x = 4 x *= 2; // x = 8 x /= 2; // x = 4</code>

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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="language-c">int age; char name[25]; // 用户输入整数： printf("你几岁了？\n"); // 显示提示信息scanf("%d", &age); // 指定数据类型和变量名printf("你%d岁了", age); // 用户输入字符串（字符数组）： printf("你的名字是？"); scanf("%s", name); printf("你好%s，你好吗？", name); /* scanf() 不读取空格，如果需要输入姓名和姓氏，可以使用fgets函数：结构： fgets(变量名, 大小, stdin) */ fgets(name, 25, stdin); // fgets 也包含结尾的'\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="language-c">#include <ctype.h> // 我们要求用户输入大写F或大写C char unit; printf("温度是摄氏度(c)还是华氏度(f)？"); scanf(" %c", &unit); // 注意%c前的空格，用于去除前导空格// 修改用户输入： unit = toupper(unit); // 现在，即使用户输入小写c或f，我们也保存大写值到unit if(unit == 'C'){ printf("温度目前是摄氏度。"); } else if (unit == 'F'){ printf("温度目前是华氏度。"); } else{ printf("%c 不是正确的值", unit); }</ctype.h></code>

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Conditional expression abbreviation

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

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

Equivalent to:

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

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

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Switch statement

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

 <code class="language-c">char grade = 'a'; // 声明变量'grade'并初始化为'a' switch (grade) { // 开始switch语句检查'grade'的值case 'a': // 如果'grade'是'a' printf("优秀!\n"); // 打印"优秀!" break; // 退出switch语句case 'b': // 如果'grade'是'b' printf("良好!\n"); // 打印"良好!" break; // 退出switch语句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.

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C language array

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

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

Core concept:

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

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

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

 <code class="language-c">int matrix[2][3] = { // 声明一个2行3列的二维数组'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="language-c">// 声明一个字符串数组'cars'，每个字符串最大长度为10个字符char cars[][10] = {"bmw", "tesla", "toyota"};</code>

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

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

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

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C language functions

Functions allow code reuse. For example:

 <code class="language-c">void greet() { printf("hello, world!\n"); printf("欢迎学习C语言编程。\n"); printf("让我们开始编码吧!\n"); } int main() { greet(); return 0; }</code>

Functions can accept parameters to make them more flexible:

 <code class="language-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.

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Structure

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

 <code class="language-c">// 定义一个名为'player'的结构体，包含两个成员struct player { char name[50]; // 字符数组'name'存储玩家姓名(最多50个字符) int score; // 整数'score'存储玩家分数}; // 创建一个'player'结构体的实例并初始化struct player player1 = {"Alice", 100}; // 初始化'player1'，姓名为"Alice"，分数为100 // 打印玩家姓名和分数printf("姓名：%s，分数：%d", player1.name, player1.score); // 输出：姓名：Alice，分数：100</code>

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

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pointer

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

 <code class="language-c">int value = 42; // 声明一个整数变量'value'并初始化为42 int *ptr = &value; // 声明一个指向整数的指针变量'ptr'并将其初始化为'value'的地址printf("值：%d，地址：%p", *ptr, ptr); // 打印'ptr'指向的值和'ptr'存储的地址</code>

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

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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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