文章目录

C语言
- 1.helloworld
- - 1.1 pause
  - 1.2 cls清屏
  - 1.3 加法运算
  - 1.4 hello
- 2 常量变量和数据类型
- - 2.1 常量
  - 2.2 变量
  - 2.3 sizeof数据类型大小
  - 2.4 无符号整型
  - 2.5 字符类型
  - - 2.5.1 字符类型简介
    - 2.5.2 字符类型运算
  - 2.6 实数型
  - 2.7 进制和转换
  - 2.8 数据溢出
- 3. 运算符和分支循环语句
- - 3.1 字符串输出
  - - 3.1.1 字符数组输出
    - 3.1.2 字符数组格式化输出(%-15s)
    - 3.1.2 字符输出 (putchar)
  - 3.2 格式化输入
  - - 3.2.1 获取单个输入
    - 3.2.2 获取多个输入
    - 3.2.3 连续相同输入
    - 3.2.4 字符数组输入
    - 3.2.5 getchar获取字符输入
  - 3.3 算数运算符
  - - 3.3.1 数学运算
    - 3.3.2 自增运算（a++与++a）
  - 3.4 逻辑运算
  - - 3.5 三目运算
    - 3.5.1 三目运算使用
    - 3.5.2 三目运算案例2
  - 3.6 隐式转换和强制类型转换
  - - 3.6.1 隐式转换
    - 3.6.2 强制类型转换
  - 3.7 if 语句
  - - 3.7.1 if …else… 语句
    - 3.7.2 else if语句
    - 3.7.3 if else if else 语句
  - 3.8 switch
  - 3.9 while 循环
  - 3.10 do while
  - - 3.10.1 do..whie语句
    - 3.10.2 水仙花数问题
- 4. for循环和数组排序
- - 4.1 for 循环
  - - 4.1.1 基础的for循环
    - 4.1.2 省略的表达式1
    - 4.1.3 省略表达式2
    - 4.1.4 省略表达式123
    - 4.1.5 多个表达式
  - 4.2 猜数字游戏
  - 4.3 模拟电子表
  - 4.4 9*9乘法表
  - - 4.4.1 正序9*9乘法表
    - 4.4.2 倒序9*9乘法表
  - 4.5 continue
  - - 4.5.1 for 循环中continue
    - 4.5.2 while循环中continue
  - 4.6 goto语句
  - - 4.6.1 goto语句简介
    - 4.6.2 循环语句中goto
  - 4.7 数组
  - - 4.7.1 数组简介
    - 4.7.2 数组大小与个数
    - 4.7.3 数组初始化
  - 4.8 数组逆序
  - 4.9 冒泡排序
- 5. 二维数组、字符串、函数
- - 5.1 二维数组
  - - 5.1.1 二维数组定义
    - 5.1.2 二维数组练习
    - 5.1.3 多维数组
  - 5.2 字符数组和字符串
  - - 5.2.1 字符数组打印
    - 5.2.2 统计字符串中每个字符出现的次数
    - 5.2.3 scanf获取字符串
  - 5.3 字符串操作函数
  - - 5.3.1 gets 函数
    - 5.3.2 fgets 函数
    - 5.3.3 puts 函数
    - 5.3.4 fputs函数
    - 5.3.5 strlen函数
    - 5.3.6 实现strlen函数
  - 5.4 字符串拼接
  - 5.5 函数
  - - 5.5.1 函数声明定义
    - 5.5.2 exit函数
- 6. 指针
- - 6.1 指针基础
- 6.2 野指针和空指针
- - - 6.2.1 野指针
    - 6.2.2 空指针
  - 6.3 泛型指针(void **)
  - 6.4 const作用
  - - 6.4.1 修饰变量
    - 6.4.2 const int *p
    - 6.4.3 int const *p
    - 6.4.4 int * const p
    - 6.4.5 const int * const p
  - 6.5 指针和数组
  - - 6.5.1 数组操作
    - 6.5.2 指针操作
  - 6.6 指针算法运算
  - - 6.6.1 指针+-操作
    - 6.6.2 &数组名 +1操作
    - 6.6.3 指针加减操作
    - 6.6.4 strlen实现方式（指针）
  - 6.7 指针的比较运算
  - 6.8 指针数组
  - 6.9 多级指针
- 7. 指针和字符串
- - 7.1 传值和传址
  - 7.2 数组做函数参数
  - 7.3 指针做函数返回值
  - 7.4 指针和字符串
  - 7.5 字符串比较
  - 7.6 字符串拷贝
  - 7.7 字符串中查找字符
  - 7.8 字符串去除空格
  - 7.9 字符串中找子串
- 8. 字符串和内存
- - 8.1 字符串操作
  - - 8.1.1 非空字符串元素个数
    - 8.1.2 字符串逆序
    - 8.1.3 字符串拷贝
    - 8.1.4 字符串拼接strcat和strncat
    - 8.1.5 strcmp和strcmpz
    - 8.1.6 格式化度读入和写出sprintf,sscanf
    - 8.1.7 字符串分割strtok
    - 8.1.8 atol_atof_atol
  - 8.2 局部变量
  - 8.3 申请堆空间
  - 8.4 二级指针malloc空间
- 9. 文件
- - 9.1 联合体和枚举
  - - 9.1.1 联合体
    - 9.1.2 枚举
  - 9.2 系统文件
  - 9.3 文件的打开和关闭
  - 9.4 fput和fget
  - 9.5 feof
  - 9.6 fgets和fputs
  - 9.7 四则运算（文件版）
  - 9.8 sprintf和sscanf
  - 9.9 文件版随机排序
  - 9.10 结构化读取fwrite和fread
  - 9.11 大文件拷贝
  - 9.12 随机读取文件
  - - 9.12.1 fseek
    - 9.12.2 改变指针位置
    - 9.12.3 读取指针位置
  - 9.13 获取文件属性
  - 9.14 缓存区刷新

C语言

1.helloworld

1.1 pause

#include // #:关键标识符，表示引入头文件； include：引入头文件关键字// stdio.h: 系统标准输入、输出库对应的头文件。 给printf函数服务。//: 使用系统库函数。"": 用户自定义库函数。int main(void)//int: 函数返回值是整型数据。mian：函数名。程序唯一的入口。必须有，且只有一次。 void：函数调用无需传参。{// 函数体 起始位置printf("hello world!\n");// 将 “hellow world”写到屏幕上。 \n: 回车换行system("pause");// 调用 syatem 函数， 实现暂停功能。 return 0;// 返回当前函数调用 --- 退出程序。0 要跟 main函数的返回值一一对应。}// 函数体 结束位置

1.2 cls清屏

#include #include int main(void)//int: 函数返回值是整型数据。mian：函数名。程序唯一的入口。必须有，且只有一次。 void：函数调用无需传参。{// 函数体 起始位置printf("-----------hello world!\n");// 将 “hellow world”写到屏幕上。 \n: 回车换行Sleep(2000);system("cls");// 调用 syatem 函数， 实现清屏功能。 return 0;// 返回当前函数调用 --- 退出程序。0 要跟 main函数的返回值一一对应。}

1.3 加法运算

#include int main(void){int a = 3;// 定义 整型变量 a， 赋初值 3int b = 5;// 定义 整型变量 b， 赋初值 5int c;// 定义 整型变量 c， 无初值c = a + b;// a + b ,将结果 赋值 给 cprintf("hello world\n");// %d:格式匹配符，匹配整型数据printf("%d\n", c /*注释*/ );printf("c = %d\n", c);printf("%d + %d = %d\n", a, b, c);printf("%d + %d = &d\n", a, b, a+b);return 0;}

1.4 hello

#include #define PI 3.14// 定义常量 PI宏定义// 我是一个单行注释君int main(void){printf("helloworld\n");/*wo shi 一个多行注释 sir*/printf("%d\n, PI");return 0;}

2 常量变量和数据类型

2.1 常量

#include #define PI 3.1415// 常量int main(void){// 圆的面积s = PI x 半径的平方// 圆的周长l = 2 * PI * r//int r = 3;// 变量const int r = 3;// 只读变量float s = PI * r * r;float l = 2 * PI * r;//printf("圆的周长为：%f\n", l);//18.849001//printf("圆的面积为：%f\n", s);//28.273500printf("圆的周长为：%.2f\n", l);// 指定小数点后保留2位, 对第3位做，4舍五入printf("圆的面积为：%.2f\n", s);// 指定小数点后保留2位return 0;}

2.2 变量

#include int main(void){int a; // 显示的做变量a的声明a = 56;// 变量使用、变量赋值。return 0;}

2.3 sizeof数据类型大小

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include #define N 1024// 定义常量int main(void){int a = 10;// 定义变量： 三要素short b = 20;long c = 30;long long d = 40;printf("================a===%d\n", sizeof(a));printf("================b===%d\n", sizeof(b));printf("================c===%d\n", sizeof(c));printf("================d===%d\n", sizeof(d));printf("int 大小为：%d\n", sizeof(int));printf("short 大小为：%d\n", sizeof(short));printf("long 大小为：%d\n", sizeof(long));printf("long long 大小为：%d\n", sizeof(long long));system("pause");return EXIT_SUCCESS;}

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include #define N 1024// 定义常量int main(void){int a = 3;short b = 4;long c = 5;// 5L5llong long d = 6;// 5LL5llprintf("sizeof(int) = %d\n", sizeof(int));printf("sizeof(short) = %d\n", sizeof(short));printf("sizeof(long) = %d\n", sizeof(long));printf("sizeof(long long) = %d\n", sizeof(long long));printf("--------------------------------------\n");unsigned int aun = 3;// 3uunsigned short bun = 4;// 3uunsigned long cun = 5;// 3luunsigned long long dun = 6;// 3lluprintf("sizeof(unsigned int) = %d\n", sizeof(unsigned int)); // aunprintf("sizeof(unsigned short) = %d\n", sizeof(unsigned short));printf("sizeof(unsigned long) = %d\n", sizeof(unsigned long));printf("sizeof(unsigned long long) = %d\n", sizeof(unsigned long long));}

2.4 无符号整型

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){size_t var = 10;printf("var = %u\n", var);unsigned int a = 10u;// 简写成 unsigned int a = 10;unsigned short b = 20u;// 简写成 unsigned short b = 20;unsigned long c = 30Lu; unsigned long long d = 40LLu;printf("unsigned int 型数据值：%u\n", a);printf("unsigned short 型数据值：%hu\n", b);printf("unsigned long 型数据值：%lu\n", c);printf("unsigned long long 型数据值：%llu\n", d);system("pause");return EXIT_SUCCESS;}

2.5 字符类型

2.5.1 字符类型简介

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){char ch = 'A';// 65//printf("1 ch = %c\n", ch);printf("1 ch = %d\n", ch);ch = 'm'; ////printf("2 ch = %c\n", ch);printf("2 ch = %d\n", ch);//ch = 97;ch = 'a';// 97//printf("3 ch = %c\n", ch);printf("3 ch = %d\n", ch);system("pause");return EXIT_SUCCESS;}

2.5.2 字符类型运算

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // A -- 65 a -- 97 int main(void){char ch = 'M';char var = '5';printf("ch = %c\n", ch + 32);printf("var = %c\n", var + 4);printf("'\\n\'的值为=%d\n", '\n');system("pause");return EXIT_SUCCESS;}

2.6 实数型

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){float m = 3.145;double n = 4.566545;printf("m = %08.2f\n", m);printf("n = %08.3lf\n", n);system("pause");return EXIT_SUCCESS;}

2.7 进制和转换

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){int a = 0x2C;// 等价 0x2c printf("10进制显示 a = %d\n", a);printf("8进制显示 a = %o\n", a);printf("16进制显示 a = %x\n", a);system("pause");return EXIT_SUCCESS;}

2.8 数据溢出

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){char ch = 127+1;// -128 -- 127printf("ch = %d\n", ch);system("pause");return EXIT_SUCCESS;}

3. 运算符和分支循环语句

3.1 字符串输出

3.1.1 字符数组输出

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){char ch = 'a';printf("ch = %c\n", ch);char str[20] = "hello world";printf("str = %s\n", str);system("pause");return EXIT_SUCCESS;}

3.1.2 字符数组格式化输出(%-15s)

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){char str[] = "hello world";printf("str = |%-15s|\n", str);system("pause");return EXIT_SUCCESS;}

3.1.2 字符输出 (putchar)

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){putchar(97);// 'a' == 97putchar('b');putchar('c');putchar('d');putchar('abcZ');system("pause");return EXIT_SUCCESS;}

3.2 格式化输入

3.2.1 获取单个输入

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // 获取用户输入 整数int main(void){int a;scanf("%d", &a);// &：表示取出变量a的地址。描述a的空间printf("a = %d\n", a);system("pause");return EXIT_SUCCESS;}

3.2.2 获取多个输入

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // 获取用户输入 整数int main(void){char ch1, ch2, ch3;//连续定义同类型多个变量。scanf("%c%c%c", &ch1, &ch2, &ch3);// &：表示取出变量ch的地址。描述a的空间printf("ch1 = %c\n", ch1);printf("ch2 = %c\n", ch2);printf("ch3 = %c\n", ch3);system("pause");return EXIT_SUCCESS;}

3.2.3 连续相同输入

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // 获取用户输入 整数int main(void){int a1, a2, a3;//连续定义同类型多个变量。scanf("%d %d %d", &a1, &a2, &a3);// &：表示取出变量ch的地址。描述a的空间printf("a1 = %d\n", a1);printf("a2 = %d\n", a2);printf("a3 = %d\n", a3);system("pause");return EXIT_SUCCESS;}

3.2.4 字符数组输入

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // 获取用户输入 整数int main(void){char a[5];// 大小为5字节的数组scanf("%s", a);// 接收用户键盘输入，写入数组a中printf("a = %s\n", a);system("pause");return EXIT_SUCCESS;}

3.2.5 getchar获取字符输入

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // 获取用户输入 整数int main(void){char ch;ch = getchar();// 接收用户输入，返回接收到的ASCII码printf("ch = %c\n", ch);putchar(ch);putchar('\n');system("pause");return EXIT_SUCCESS;}

3.3 算数运算符

3.3.1 数学运算

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){int a = 10;int b = 20;int c = a * b;int d = 34 / 10;// 0.5//int m = 98 / 0;printf("d = %d\n", d);system("pause");return EXIT_SUCCESS;}

3.3.2 自增运算（a++与++a）

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){int a = 10;int b = 50;printf("a = %d\n", a++);// 先取值给%d, 在自增printf("----a = %d", a);printf("b = %d\n", ++b);// 先自增,再取值。 printf("----b = %d\n", b);system("pause");return EXIT_SUCCESS;}

3.4 逻辑运算

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){int a = 34;int b = 0;char str[10] = "hello";++str[0];printf("a = %d\n", !a);printf("b = %d\n", !b);printf("======%d\n", a && !b);printf("------%d\n", !a || b);system("pause");return EXIT_SUCCESS;}

3.5 三目运算

3.5.1 三目运算使用

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // int main(void){int a = 40;int b = 4;int m = a  b ? 69 : 100);system("pause");return EXIT_SUCCESS;}

3.5.2 三目运算案例2

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // int main(void){int a = 10, b = 20, c = 30;int x = (a = 1, c = 5, b = 2);printf("x = %d\n", x);printf("a = %d\n", a);printf("b = %d\n", b);printf("c = %d\n", c);system("pause");return EXIT_SUCCESS;}

3.6 隐式转换和强制类型转换

3.6.1 隐式转换

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // 隐式类型转换。int main(void){int a = 321;char ch = a;printf("ch = %d\n", ch);// 字符类型转换为整数类型system("pause");return EXIT_SUCCESS;}

3.6.2 强制类型转换

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // 强制类型转换int main(int var){//int *p = (int *)malloc(100);float price = 3.6;int weight = 4;//double sum = (int)price * weight;double sum = (int)(price * weight);printf("价格：%lf\n", sum);system("pause");return EXIT_SUCCESS;}

3.7 if 语句

3.7.1 if …else… 语句

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){int a;scanf("%d", &a);if (a > 0){printf("a > 0\n");}else{printf("a <= 0\n");}system("pause");return EXIT_SUCCESS;}

3.7.2 else if语句

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){int score;// 100--90 优 90 -- 70 良好 70 -- 60 及格< 60 差劲printf("请输入学生成绩：");scanf("%d", &score);if (score >= 90 && score <= 100){printf("优秀\n");}else if (score < 90 && score >= 70){printf("良好\n");}else if (score < 70 && score >= 60){printf("及格\n");}else{printf("不及格\n");}system("pause");return EXIT_SUCCESS;}

3.7.3 if else if else 语句

int main0703(void){int pig1, pig2, pig3;// if (pig1 > pig2 && pig1 > pig3)// pig1 > pig2 " />printf("请输入三只小猪的体重:");scanf("%d %d %d", &pig1, &pig2, &pig3);if (pig1 > pig2)// 满足，说明pig1最重{if (pig1 > pig3){printf("第一只小猪最重，体重为：%d\n", pig1);}else{printf("第3只小猪最重，体重为：%d\n", pig3);}} else{if (pig2 > pig3){printf("第2只小猪最重，体重为：%d\n", pig2);}else{printf("第3只小猪最重，体重为：%d\n", pig3);}}system("pause");return EXIT_SUCCESS;}

3.8 switch

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){int score;scanf("%d", &score);switch (score / 10){case 10:// 100 -- 90 优秀case 9:printf("优秀\n");break;case 8:// 70 -- 90 良好case 7:printf("良好\n");//break;case 6: // 70 - 60 及格printf("及格\n");//break;default:printf("不及格\n");break;}system("pause");return EXIT_SUCCESS;}

3.9 while 循环

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // int main(void){int num = 1;while (num <= 100){if ((num % 7 == 0) || (num % 10 == 7) || (num / 10 == 7))// 个位、10位、7的倍数{printf("敲桌子\n");}else{printf("%d\n", num);}num++;// 递增}system("pause");return EXIT_SUCCESS;}

3.10 do while

3.10.1 do…whie语句

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // while 的基础用法int main(void){int a = 1;do{a++;printf("a = %d\n", a);} while (a < 10);system("pause");return EXIT_SUCCESS;}

3.10.2 水仙花数问题

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // 水仙花数：一个三位数。各个位上的数字的立方和等于本数字。 int main(void){int a, b, c;int num = 100;do {a = num % 10;// 个位b = num / 10 % 10;// 十位c = num / 100;// 百位if (a*a*a + b*b*b + c*c*c == num){printf("%d\n", num);}num++;} while (num < 1000);system("pause");return EXIT_SUCCESS;}

4. for循环和数组排序

4.1 for 循环

4.1.1 基础的for循环

#define _CRT_SECURE_NO_WARNINGS#include #include #include int main(void){srand(time(NULL));//种随机数种子。int n = 0;int num = rand() % 100;// 生成随机数for (;;)// while(1){printf("请输入猜测的数字：");scanf("%d", &n);if (n < num){// for、while、if 如果执行语句只有一条。 { } 可以省略printf("猜小了\n");}else if (n > num)printf("猜大了\n");else{printf("猜中！！！\n");break;// 跳出}}printf("本尊是：%d\n", num);system("pause");return 0;}

4.1.2 省略的表达式1

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // 基础for循环int main(void){int i = 1;// 循环因子int sum = 0;for (; i <= 100; i++){sum = sum + i;//sum += i;}printf("sum = %d\n", sum);system("pause");return EXIT_SUCCESS;}

4.1.3 省略表达式2

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // 基础for循环int main(void){int i = 1;// 循环因子int sum = 0;for (; i <= 100; ){sum = sum + i;//sum += i;i++;}printf("sum = %d\n", sum);system("pause");return EXIT_SUCCESS;}

4.1.4 省略表达式123

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // 省略表达式123，无限循环int main(void){int i = 0;// 循环因子//for (;1;)// 死循环。while(k=1)for (;;){printf("i = %d\n", i);i++;}system("pause");return EXIT_SUCCESS;}

4.1.5 多个表达式

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // 表达式有多个int main(void){int i = 0;int a = 0;for (i = 1, a = 3; a < 20; i++){printf("i = %d\n", i);printf("a = %d\n", a);a += 5;}system("pause");return EXIT_SUCCESS;}

4.2 猜数字游戏

#define _CRT_SECURE_NO_WARNINGS#include #include #include int main(void){srand(time(NULL));//种随机数种子。int n = 0;int num = rand() % 100;// 生成随机数for (;;)// while(1){printf("请输入猜测的数字：");scanf("%d", &n);if (n < num){// for、while、if 如果执行语句只有一条。 { } 可以省略printf("猜小了\n");}else if (n > num)printf("猜大了\n");else{printf("猜中！！！\n");break;// 跳出}}printf("本尊是：%d\n", num);system("pause");return 0;}

4.3 模拟电子表

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include #include int main(void){int i, j, k;// 小时for (i = 0; i < 24; i++){// 分钟for (j = 0; j < 60; j++){// 秒for (k = 0; k < 60; k++){printf("%02d:%02d:%02d\n", i, j, k);Sleep(960);system("cls");// 清屏}}}system("pause");return EXIT_SUCCESS;}

**4.4 9*9乘法表**

**4.4.1 正序9*9乘法表**

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // 正序99乘法表int main(void){for (size_t i = 1; i <= 9; i++){for (size_t j = 1; j <= i; j++){printf("%dx%d=%d\t", j, i, j * i);}printf("\n");}system("pause");return EXIT_SUCCESS;}

**4.4.2 倒序9*9乘法表**

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // 倒序 99 乘法表int main(void){int i, j;for (i = 9; i >= 1; i--)// 行{for (j = 1; j <= i; j++)// 列{printf("%dx%d=%d\t", j, i, j * i);}putchar('\n');}system("pause");return EXIT_SUCCESS;}

4.5 continue

4.5.1 for 循环中continue

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){for (size_t i = 0; i < 5; i++){if (i == 3){continue;}printf("i = %d\n", i);printf("============1=========\n");printf("============2=========\n");printf("=============3========\n");printf("============4=========\n");printf("=============5========\n");}system("pause");return EXIT_SUCCESS;}

4.5.2 while循环中continue

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){int num = 5;//while (num--)// 当num自减为 0 时循环终止。等价于 while (num-- != 0)while (num-- != 0) // 当num自减为 0 时循环终止。{printf("num = %d\n", num);if (num == 3){continue;}printf("============1=========\n");printf("============2=========\n");printf("=============3========\n");printf("============4=========\n");printf("=============5========\n");}system("pause");return EXIT_SUCCESS;}

4.6 goto语句

4.6.1 goto语句简介

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){printf("============1==========\n");printf("============2==========\n");goto LABLE;printf("============3==========\n");printf("============4==========\n");printf("============5==========\n");printf("============6==========\n");printf("============7==========\n");LABLE:printf("============8==========\n");printf("============9==========\n");printf("============10==========\n");system("pause");return EXIT_SUCCESS;}

4.6.2 循环语句中goto

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){int i = 0;for (i = 0; i < 10; i++){if (i == 5)goto ABX234;printf("i = %d\n", i);}for (int j = 0; j < 20; j++){ABX234:printf("j = %d\n", j);}system("pause");return 0;}

4.7 数组

4.7.1 数组简介

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){int a = 5, b = 29, c = 10;int arr[10] = { 1, 2 ,4, 6, 76, 8, 90 ,4, 3, 6 };//int a = 109;printf("&arr[0] = %p\n", &arr[0]);// 取数组首元素的地址printf("arr = %p\n", arr);// 数组名system("pause");return EXIT_SUCCESS;}

4.7.2 数组大小与个数

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){int a = 5, b = 29, c = 10;int arr[12] = { 1, 2 ,4, 6, 76, 8, 90 ,4, 3, 6 , 6, 8 };//int a = 109;printf("数组大小：%u\n", sizeof(arr));printf("数组元素的大小：%u\n", sizeof(arr[0]));printf("数组元素个数：%d\n", sizeof(arr) / sizeof(arr[0]));system("pause");return EXIT_SUCCESS;}

4.7.3 数组初始化

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // 数组初始化int main(void){int arr[10];//int a = 109;arr[0] = 5;arr[1] = 6;arr[2] = 7;int n = sizeof(arr) / sizeof(arr[0]);for (size_t i = 0; i < n; i++){printf("%d\n", arr[i]);}system("pause");return EXIT_SUCCESS;}

4.8 数组逆序

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // 数组元素逆序int main(void){int arr[] = { 1, 6, 8, 0, 4, 3, 9, 2 };// {2, 9, 3, 4, 0, 8, 6, 1}int len = sizeof(arr) / sizeof(arr[0]); //数组元素个数int i = 0;// i表示数组的首元素下标int j = len - 1;// 表示数组的最后一个元素下标int temp = 0;// 临时变量 // 交换 数组元素，做逆序while (i < j){temp = arr[i];// 三杯水法变量交换arr[i] = arr[j];arr[j] = temp;i++;j--;}// 打印交互后的 数组for (size_t n = 0; n < len; n++){printf("%d ", arr[n]);}printf("\n");system("pause");return EXIT_SUCCESS;}

4.9 冒泡排序

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){int arr[] = { 12, 32, 14, 62, 27, 8, 89 };int n = sizeof(arr) / sizeof(arr[0]);// 数组元素个数int temp = 0;// 临时变量for (size_t i = 0; i < n; i++){printf("%d ", arr[i]);}printf("\n");// 完成乱序数组的冒泡排序。for (size_t i = 0; i < n - 1; i++)// 外层控制行{for (size_t j = 0; j < n - 1 - i; j++)// 内层控制列{if (arr[j] > arr[j + 1])// 满足条件 三杯水交换{temp = arr[j];arr[j] = arr[j + 1];arr[j + 1] = temp;}}}// 打印排序后的数组，确定正确性。for (size_t i = 0; i < n; i++){printf("%d ",arr[i]);}printf("\n");system("pause");return EXIT_SUCCESS;}

5. 二维数组、字符串、函数

5.1 二维数组

5.1.1 二维数组定义

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){int arr[3][4] = { {2, 7, 8, 5},{75, 8, 9, 8},{26, 37, 99, 9} };for (size_t i = 0; i < 3; i++)//行{for (size_t j = 0; j < 4; j++)//列{printf("%d ", arr[i][j]);}printf("\n");}printf("数组的大小为：%u\n", sizeof(arr));printf("数组行的大小：%u\n", sizeof(arr[0]));printf("数组一个元素的大小：%u\n", sizeof(arr[0][0]));printf("行数=总大小/一行大小：%d\n", sizeof(arr) / sizeof(arr[0]));printf("列数=行大小/一个元素大小：%d\n", sizeof(arr[0]) / sizeof(arr[0][0]));printf("arr= %p\n", arr);printf("&arr[0] = %p\n", &arr[0][0]);printf("arr[0] = %p\n", arr[0]);system("pause");return EXIT_SUCCESS;}

5.1.2 二维数组练习

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){/*56 78 9245 67 9329 83 8893 56 8972 83 81*/int scores[5][3] = { 1, 2, 4, 5, 6, 7, 8, 9 };int row = sizeof(scores) / sizeof(scores[0]);int col = sizeof(scores[0]) / sizeof(scores[0][0]);// 获取 5 名学生、3门功课成绩for (size_t i = 0; i < row; i++){for (size_t j = 0; j < col; j++){scanf("%c", &scores[i][j]);}}// 求一个学生的总成绩for (size_t i = 0; i < row; i++) // 每个学生{int sum = 0;for (size_t j = 0; j < col; j++)// 每个学生的成绩{sum += scores[i][j];}printf("第%d个学生的总成绩为：%d\n", i + 1, sum);}//求一门功课的总成绩for (size_t i = 0; i < col; i++)// 第几门功课{int sum = 0;for (size_t j = 0; j < row; j++)// 每门功课的第几个学生{sum += scores[j][i];}printf("第%d门功课的总成绩为：%d\n", i + 1, sum);}system("pause");return EXIT_SUCCESS;}

5.1.3 多维数组

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){int a[3][4][2] ={{{1, 2},{2, 3},{4, 5},{5, 6}},{{45, 67},{78, 90},{12, 6},{45, 9}},{{ 45, 67 },{ 78, 90 },{ 12, 6 },{ 45, 9 }}};//int arr[2][3][5] = {1, 2, 4, 5, 6, 7, 8 , 9, 0, 0, 7, 9, 8};for (size_t i = 0; i < 3; i++){for (size_t j = 0; j < 4; j++){for (size_t k = 0; k < 2; k++){printf("%d ", a[i][j][k]);}printf("\n");}printf("\n\n");}system("pause");return EXIT_SUCCESS;}

5.2 字符数组和字符串

5.2.1 字符数组打印

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){char str[6] = { 'h', 'e', 'l', 'l', 'o', '\0' };char str2[] = "world";//== {'w', 'o', 'r', 'l', 'd', '\0'}printf("%s\n", str2);system("pause");return EXIT_SUCCESS;}

5.2.2 统计字符串中每个字符出现的次数

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){char str[11] = { 0 };// helloworld -->26个英文字母 a-za:97 d:100// scanf("%s", str);for (size_t i = 0; i < 10; i++){scanf("%c", &str[i]);}int count[26] = { 0 };// 代表26个英文字母出现的次数。 for (size_t i = 0; i < 11; i++){int index = str[i] - 'a';// 用户输入的字符在 count数组中的下标值。count[index]++;}for (size_t i = 0; i < 26; i++){if (count[i] != 0){printf("%c字符在字符串中出现 %d 次\n", i + 'a', count[i]);}}system("pause");return EXIT_SUCCESS;}

5.2.3 scanf获取字符串

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){char str[100];//scanf("%s", str);scanf("%[^\n]s", str);printf("%s\n", str);system("pause");return EXIT_SUCCESS;}

5.3 字符串操作函数

5.3.1 gets 函数

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include //getsint main(void){char str[10];printf("请输入字符串：");gets(str);printf("%s\n", str);system("pause");return EXIT_SUCCESS;}

5.3.2 fgets 函数

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){char str[10];printf("获取的字符串为：%s", fgets(str, sizeof(str), stdin));system("pause");return EXIT_SUCCESS;}

5.3.3 puts 函数

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include //putsint main(void){char str[] = "hello world\n";int ret = puts(str);// puts("hello world");printf("ret = %d\n", ret);system("pause");return EXIT_SUCCESS;}

5.3.4 fputs函数

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include //fputsint main(void){char str[] = "hello world\n";//int ret = fputs(str, stdout);// int ret = fputs("hello world\n", stdout);printf("ret = %d\n", ret);system("pause");return EXIT_SUCCESS;}

5.3.5 strlen函数

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include //fputs// strlen() 函数 ： 获取字符串的 有效长度： 不包含\0int main(void){char str[] = "hello\0world";printf("sizeof(str) = %u\n", sizeof(str));printf("strlen(str) = %u\n", strlen(str));system("pause");return EXIT_SUCCESS;}

5.3.6 实现strlen函数

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include //fputsint main(void){char str[] = "hello world";int i = 0;while (str[i] != '\0'){i++;}printf("%d\n", i);// 等价于 printf("%d\n", strlen(str));system("pause");return EXIT_SUCCESS;}

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // 进阶版int main(void){char str[] = "hello\0world";int i = 0;while (str[i++]);printf("%d\n", i - 1);// 等价于 printf("%d\n", strlen(str));system("pause");return EXIT_SUCCESS;}

5.4 字符串拼接

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){char str1[] = "hello";// [ h e l l o \0 ]char str2[] = "world";char str3[100];int i = 0;// 循环 str1while (str1[i] != '\0') // '\0' != '\0'{str3[i] = str1[i];// 循环着将str1中的每一个元素，交给str3i++;}// str3=[h e l l o]//printf("%d\n", i);--> 5int j = 0;// 循环 str2while (str2[j]) // 等价于 while(str2[j] !='\0') 等价于 while(str2[j] != 0){str3[i + j] = str2[j];j++;}// str3=[h e l l o w o r l d]// 手动添加 \0 字符串结束标记str3[i + j] = '\0';printf("str3 = %s\n", str3);system("pause");return EXIT_SUCCESS;}

5.5 函数

5.5.1 函数声明定义

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include void bubble_sort(int arr[]);// 函数声明 int arr[] 函数形参void print_arr(int arr[]);int main(void){printf("add = %d\n", add(2, 6));int arr[] = { 54, 5, 16, 34 , 6, 9, 34, 1, 7, 93 };bubble_sort(arr);print_arr(arr);system("pause");return EXIT_SUCCESS; // 底层 调用 _exit(); 做退出}void print_arr(int arr[]){for (size_t i = 0; i < 10; i++){printf("%d ", arr[i]);}}void bubble_sort(int arr[]){int i, j, temp;for (i = 0; i < 10 - 1; i++){for (j = 0; j < 10 - 1 - i; j++){if (arr[j] < arr[j + 1]){temp = arr[j];arr[j] = arr[j + 1];arr[j + 1] = temp;}}}}int add(int a, int b){return a + b;}

5.5.2 exit函数

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int func(int a, char ch);int main(void){int ret = func(10, 'a');printf("ret = %d\n", ret);system("pause");//return EXIT_SUCCESS;exit(EXIT_SUCCESS);}int func(int a, char ch){printf("a = %d\n", a);printf("ch = %c\n", ch);//return 10;exit(10);}

6. 指针

6.1 指针基础

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){int a = 10;int* p = &a;//*p = 2000;a = 350;//printf("a = %d\n", a);printf("*p = %d\n", *p);printf("sizeof(int *) = %u\n", sizeof(int*));printf("sizeof(short *) = %u\n", sizeof(short*));printf("sizeof(char *) = %u\n", sizeof(char*));printf("sizeof(long *) = %u\n", sizeof(long*));printf("sizeof(double *) = %u\n", sizeof(double*));printf("sizeof(void *) = %u\n", sizeof(void*));system("pause");return EXIT_SUCCESS;}

6.2 野指针和空指针

6.2.1 野指针

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // 野指针1int main(void){int *p;*p = 2000;printf("*p = %d\n", *p);system("pause");return EXIT_SUCCESS;}

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // 野指针2int main(void){int m;//int *p = 1000; // 0-255 确定留给操作系统int *p = 0x0bfcde0000;p = &m;*p = 2000;printf("*p = %d\n", *p);system("pause");return EXIT_SUCCESS;}

6.2.2 空指针

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // 空指针int main(void){int *p = NULL; // NULL == 0// .....// lllll// .....if (p != NULL){*p = 300;printf("*p = %d\n", *p);}system("pause");return EXIT_SUCCESS;}

6.3 泛型指针(void )**

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){int a = 345;char ch = 'R';void* p;// 万能指针、泛型指针//p = &a;p = &ch;printf("%c\n", *(char*)p);system("pause");return EXIT_SUCCESS;}

6.4 const作用

6.4.1 修饰变量

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // 修饰变量int main(void){const int a = 20;int* p = &a;*p = 650;printf("%d\n", a);system("pause");return EXIT_SUCCESS;}

**6.4.2 const int *p**

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // const int *p;int main(void){int a = 10;int b = 30;const int* p = &a;//*p = 500;p = &b;printf("*p=%d", *p);system("pause");return EXIT_SUCCESS;}

**6.4.3 int const *p**

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){int a = 10;int b = 30;int const* p = &a;//*p = 300;p = &b;printf("*p=%d", *p);system("pause");return EXIT_SUCCESS;}

**6.4.4 int * const p**

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){int a = 10;int b = 30;int* const p = &a;*p = 300;//p = &b;printf("a = %d\n", *p);printf("a = %d\n", a);system("pause");return EXIT_SUCCESS;}

**6.4.5 const int * const p**

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){int a = 10;int b = 30;const int* const p = &a;//*p = 300;//p = &b;printf("a = %d\n", *p);printf("a = %d\n", a);system("pause");return EXIT_SUCCESS;}

6.5 指针和数组

6.5.1 数组操作

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // 操作数组元素的 4 种方法int main(void){int a[] = { 1, 2, 4, 5, 6, 7, 8, 9, 0 };int n = sizeof(a) / sizeof(a[0]);int* p = a;printf("sizeof(a) = %u\n", sizeof(a));printf("sizeof(p) = %u\n", sizeof(p));for (size_t i = 0; i < n; i++){//printf("%d "), a[i];//printf("%d ", *(a+i));// a[i] == *(a+i)//printf("%d ", p[i]);printf("%d ", *(p + i));// p[i] = *(p+i)}printf("\n");system("pause");return EXIT_SUCCESS;}

6.5.2 指针操作

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // 使用指针++操作数组元素int main(void){int arr[] = { 1, 2, 4, 5, 6, 7, 8, 9, 0 };int* p = arr;int n = sizeof(arr) / sizeof(arr[0]);printf("first p = %p\n", p);for (size_t i = 0; i < n; i++){printf("%d ", *p);p++;// p = p+1; 一次加过一个int大小。 一个元素。}putchar('\n');printf("last p = %p\n", p);system("pause");return EXIT_SUCCESS;}

6.6 指针算法运算

6.6.1 指针±操作

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // 指针在数组中 +- 整数int main(void){int a[] = { 1, 2, 4, 5, 6, 7, 8, 9, 0 };//int *p = a; // a == &a[0];int* p = &a[5];printf("p-2 = %p\n", p - 2);printf("&a[3] = %p\n", &a[3]);system("pause");return EXIT_SUCCESS;}

6.6.2 &数组名 +1操作

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // &数组名 +1int main(void){short a[10] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 0 };printf("a = %p\n", a);printf("&a[0] = %p\n", &a[0]);printf("a+1 = %p\n", a + 1);printf("&a = %p\n", &a);printf("&a+1 = %p\n", &a + 1);system("pause");return EXIT_SUCCESS;}

6.6.3 指针加减操作

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // 指针加减指针int main(void){int a[10] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 0 };int* p = a;for (size_t i = 0; i < 10; i++){printf("%d ", *p);p++;}printf("p - a = %d\n", p - a);system("pause");return EXIT_SUCCESS;}

6.6.4 strlen实现方式（指针）

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int mystrlen(char arr[]);int main(void){char abc[] = "hello world";int ret = mystrlen2(abc);// 实际参数 abcprintf("ret = %d\n", ret);system("pause");return EXIT_SUCCESS;}// 借助数组 实现 int mystrlen(char str[]){int i = 0;while (str[i] != '\0'){i++;}return i;}// 借助指针++ 实现 int mystrlen2(char str[]){char* p = str;while (*p != '\0'){p++;}return p - str;// 返回数组元素的个数。}

6.7 指针的比较运算

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){int a[] = { 1, 2, 4, 5, 6, 7, 8, 9, 0 };int *p = &a[0];if (p > a)printf("成立\n");else if (p < a)printf("不成立\n");elseprintf("== \n");system("pause");return EXIT_SUCCESS;}

6.8 指针数组

#include #include #include #include // 指针数组1int main(void){int a = 10;int b = 20;int c = 30;int* p1 = &a;int* p2 = &b;int* p3 = &c;int* arr[] = { p1, p2, p3 };// 整型指针数组arr， 存的都是整型地址。printf("*(arr[0]) = %d\n", *(*(arr + 0)));//arr[0] ==*(arr+0)printf("*(arr[0]) = %d\n", **arr);system("pause");return EXIT_SUCCESS;}

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // 指针数组2int main(void){int a[] = { 10 };int b[] = { 20 };int c[] = { 30 };int* arr[] = { a, b, c };// 整型指针数组arr， 存的都是整型地址。printf("*(arr[0]) = %d\n", *(*(arr + 0)));//arr[0] ==*(arr+0)printf("*(arr[0]) = %d\n", **arr);system("pause");return EXIT_SUCCESS;}

6.9 多级指针

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){int a = 10;int* p = &a;int** pp = &p;// int **pp = &(&a); 不允许！！int*** ppp = &pp;printf("***ppp = %d\n", ***ppp);printf("**pp = %d\n", **pp);printf("*p = %d\n", *p);printf("a = %d\n", a);system("pause");return EXIT_SUCCESS;}

7. 指针和字符串

7.1 传值和传址

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int swap(int, int);// 函数声明int swap2(int*, int*);int main(void){int m = 23;int n = 57;printf("--before-- m = %d, n = %d\n", m, n);// 函数调用//swap(m, n);// m/n 实参swap2(&m, &n);printf("--after-- m = %d, n = %d\n", m, n);system("pause");return EXIT_SUCCESS;}int swap2(int* a, int* b)// 形参a、b， 需传地址值{int tmp = 0;tmp = *a;*a = *b;*b = tmp;return 0;}// 函数定义int swap(int a, int b)// a/b 形参{int tmp = 0;tmp = a;a = b;b = tmp;return 0;}

7.2 数组做函数参数

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include //void BubbleSort(int arr[])// void BubbleSort(int *arr)void BubbleSort(int* arr, int n){for (int i = 0; i < n - 1; i++){for (int j = 0; j < n - 1 - i; j++){if (arr[j] > arr[j + 1]){int temp = arr[j];arr[j] = arr[j + 1];arr[j + 1] = temp;}}}}int main(void){int arr[] = { 5, 89, 3, 22, 40, 31, 9, 22, 67, 28, 45, 78 };printf("main: sizeof(arr) = %d\n", sizeof(arr));int n = sizeof(arr) / sizeof(arr[0]);BubbleSort(arr, n);for (size_t i = 0; i < n; i++){printf("%d ", arr[i]);}printf("\n");system("pause");return EXIT_SUCCESS;}

7.3 指针做函数返回值

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int m = 100; // 全局变量 对应空间消失 ==> 程序结束。int* test_func2(int a, int b){int p = 1234;// 局部变量//return &m;return &p;}int main(void){int* ret = NULL;// NULL == 0ret = test_func2(10, 20);printf("ret = %d\n", *ret);system("pause");return EXIT_SUCCESS;}

7.4 指针和字符串

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){char str1[] = "hello";// {'h',, 'e', 'l', 'l', 'o', '\0'}char m[] = "hello";char* str2 = "hello";// "hello" 是一个字符串常量, 不能修改。char* n = "hello";str1[0] = 'R';str2[0] = 'R';printf("str1 = %p\n", str1);printf("m = %p\n", m);printf("str2 = %p\n", str2);printf("n = %p\n", n);system("pause");return EXIT_SUCCESS;}

7.5 字符串比较

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // str1 和 str2== -->0str1 > str2 --> 1, str1 -1int mystrcmp(char *str1, char *str2){int i = 0;while (str1[i] == str2[i]) // *(str1+i) == *(str2+i){if (str1[i] == '\0'){return 0;// 2字符串一样。}i++;}return str1[i] > str2[i] " />1 : -1;}int mystrcmp2(char *str1, char *str2){while (*str1 == *str2) // *(str1+i) == *(str2+i){if (*str1 == '\0'){return 0;// 2字符串一样。}str1++;str2++;}return *str1 > *str2 ? 1 : -1;}int main(void){char *str1 = "helloz";char *str2 = "helloz";//int ret = mystrcmp(str1, str2);int ret = mystrcmp2(str1, str2);if (ret == 0)printf("相同\n");else if (ret == 1)printf("str1 > str2\n");else if (ret == -1)printf("str1 < str2\n");elseprintf("异常\n");system("pause");return EXIT_SUCCESS;}

7.6 字符串拷贝

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // src: 源dst： 目标//数组版本void mystrcpy(char* src, char* dst){int i = 0;while (src[i] != 0)// src[i] == *(src+i){dst[i] = src[i];i++;}dst[i] = '\0';}//指针版void mystrcpy2(char* src, char* dst){while (*src != '\0')// src[i] == *(src+i){*dst = *src;src++;dst++;}*dst = '\0';}int main(void){char* src = "helloworldfuoie11ll";char dst[100];mystrcpy2(src, dst);printf("dst = %s\n", dst);system("pause");return EXIT_SUCCESS;}

7.7 字符串中查找字符

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // hellowrld --- 'm'char* myStrch(char* str, char ch){while (*str){if (*str == ch){return str;}str++;}return NULL;}// hellowrld --- 'o'char* myStrch2(char* str, char ch){int i = 0;while (str[i]){if (str[i] == ch){return &str[i];}i++;}return NULL;}int main(void){char str[] = "hello world";char ch = ' ';char* ret = NULL;ret = myStrch2(str, ch);printf("ret = %s\n", ret);system("pause");return EXIT_SUCCESS;}

7.8 字符串去除空格

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include void str_no_space(char* src, char* dst){int i = 0;int j = 0; while (src[i] != 0){if (src[i] != ' '){dst[j] = src[i];j++;}i++;}dst[j] = '\0';}void str_no_space2(char* src, char* dst){while (*src != 0){if (*src != ' '){*dst = *src;dst++;}src++;}*dst = '\0';}int main(void){char str[] = "ni chou sha chou ni za di";char dst[100] = { 0 };str_no_space2(str, dst);printf("dst = %s\n", dst);system("pause");return EXIT_SUCCESS;}

7.9 字符串中找子串

#include #include #include //strstr函数测试int main(void){char* ret = strstr("hellollollo", "llo");printf("ret = %s\n", ret);system("pause");return EXIT_SUCCESS;}

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int str_times(char* str, char* substr){int count = 0;char* p = strstr(str, substr);// "llollollo"while (p != NULL){count++;p += strlen(substr);// p = p+strlen(substr) --> "llollo"p = strstr(p, substr);// 返回： "llo"}return count;}// 统计字符串中，子串出现的次数。int main(void){char str[] = "helloabclloxyzllo";char substr[] = "llo";int ret = str_times(str, substr);printf("出现%d次\n", ret);system("pause");return EXIT_SUCCESS;}

8. 字符串和内存

8.1 字符串操作

8.1.1 非空字符串元素个数

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int no_space_str(char* str){int count = 0;char* p = str;while (*p){if (*p != ' '){count++;}p++;}return count;}int main(void){char str[] = "ni chou sha";int ret = no_space_str(str);printf("%d\n", ret);system("pause");return EXIT_SUCCESS;}

8.1.2 字符串逆序

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // o e l l h// // 字符串逆序void str_inserse(char* str){//int i, j;// str[i] *(str+i)char* start = str;// 记录首元素地址char* end = str + strlen(str) - 1;// 记录最后一个元素地址。while (start < end)// 首元素地址是否 < 最后一个元素地址{char tmp = *start;// 三杯水 char 元素交换*start = *end;*end = tmp;start++;// 首元素对应指针后移end--;// 尾元素对应指针前移}}// 判断回文字符串 abcddpbaint str_abcbb(char* str){char* start = str;// 记录首元素地址char* end = str + strlen(str) - 1;// 记录最后一个元素地址。while (start < end)// 首元素地址是否 < 最后一个元素地址{if (*start != *end)// 判断字符是否一致。{return 0; // 0 表示非 回文}start++;end--;}return 1;// 1 表示 回文}int main(void){char str[] = "this is a test";str_inserse(str);printf("str=%s\n ---------------------\n", str);char s2[] = "abcmncba";int ret = str_abcbb(s2);if (ret == 0)printf("不是回文\n");else if (ret == 1)printf("是回文\n");system("pause");return EXIT_SUCCESS;}

8.1.3 字符串拷贝

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // strcpyint main(void){char src[] = "abc efgzhansan wangwu ";char dest[10] = { 0 };char* p = strcpy(dest, src); printf("p= %s\n", p);printf("dest = %s\n", dest);system("pause");return EXIT_SUCCESS;}

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // strcpy// strncpyint main(void){char src[] = "hello world";char dest[100] = { 0 };char* p = strncpy(dest, src, 100); for (size_t i = 0; i < 10; i++){printf("%c\n", p[i]);}printf("p= %s\n", p);printf("dest = %s\n", dest);system("pause");return EXIT_SUCCESS;}

8.1.4 字符串拼接strcat和strncat

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){char src[] = "world";char dest[] = "hello";char* p = strcat(dest, src);printf("p = %s\n", p);printf("dest = %s\n", dest);system("pause");return EXIT_SUCCESS;}

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){char src[] = "world";char dest[6] = "hello";char* p = strncat(dest, src, 3);printf("p = %s\n", p);printf("dest = %s\n", dest);printf("%d\n", strlen(dest));system("pause");return EXIT_SUCCESS;}

8.1.5 strcmp和strcmpz

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // strncpyint main(void){char* str1 = "helloworld";char* str2 = "helloz";printf("ret = %d\n", strcmp(str1, str2));system("pause");return EXIT_SUCCESS;}

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // strncpyint main(void){char* str1 = "helloworld";char* str2 = "helloz";printf("ret = %d\n", strncmp(str1, str2, 8));system("pause");return EXIT_SUCCESS;}

8.1.6 格式化度读入和写出sprintf,sscanf

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // sprintfint main(void){char buf[100] = { 0 }; //bufferstring strsource srcsprintf(buf, "%d%c%d=%d\n", 10, '+', 34, 10 + 34);puts(buf);system("pause");return EXIT_SUCCESS;}

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include // sscanfint main(void){char buf[100] = { 0 }; //bufferstring strsource srcint a, b, c;char str[] = "13+56=89";sscanf(str, "%d+%d=%d", &a, &b, &c);printf("a = %d\n", a);printf("b = %d\n", b);printf("c = %d\n", c);system("pause");return EXIT_SUCCESS;}

8.1.7 字符串分割strtok

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){char str[] = "www.itcast.cn.com.net";// www baidu comchar* p = strtok(str, ".");// 第一次拆分，参1 传 待拆分的原串。while (p != NULL){p = strtok(NULL, ".");// 第1+ 次拆分是，参1传 NULL.printf("%s\n", p);}system("pause");return EXIT_SUCCESS;}

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){char str[] = "www.baidu.com$This is a strtok$test";char* p = strtok(str, "$ .");//strtok函数的第一个参数不为NULL，函数将找到str中第一个被分割的字符串，同时strtok还会记住该分割符的位置// strtok函数的第一个参数为NULL，函数将在之前strtok记住的分隔符的位置开始，查找下一个标记while (p != NULL){p = strtok(NULL, ". $");printf("p = %s\n", p);}system("pause");return EXIT_SUCCESS;}

8.1.8 atol_atof_atol

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include static int a = 1034673;void test1(void){static int b = 0;printf("b = %d\n", b++);}int main(void){char str[] = "abc345";int num = atoi(str);printf("num = %d\n", num);char str1[] = " -10";int num1 = atoi(str1);printf("num1 = %d\n", num1);char str2[] = "0.123f";double num2 = atof(str2);printf("num2 = %.2lf\n", num2);char str3[] = "123L";long num3 = atol(str3);printf("num3 = %ld\n", num3);system("pause");return EXIT_SUCCESS;}

8.2 局部变量

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include void test1(void);// 全局函数声明int m = 4456;int main(void){int i = 10903;for (size_t j = 0; j < 10; j++){printf("j = %d\n", j);//test1();}printf("i 2 = %d\n", i);system("pause");return EXIT_SUCCESS;}

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){//int arr[1000000] = {10, 20, 40};int *p = (int *)malloc(sizeof(int) * 10);//char *str = (char *)malloc(sizeof(char)*10);if (p == NULL){printf("malloc error\n");return -1;}char *tmp = p;// 记录malloc返回的地址值。用于free// 写数据到 malloc 空间。for (size_t i = 0; i < 10; i++){p[i] = i + 10;}// 读出malloc空间中的数据//for (size_t i = 0; i < 10; i++)//{//printf("%d ", *(p+i));//}for (size_t i = 0; i < 10; i++){printf("%d ", *p);p++;}// 释放申请的内存。free(tmp);p = NULL;system("pause");return EXIT_SUCCESS;}

8.3 申请堆空间

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){//int arr[1000000] = {10, 20, 40};int* p = (int*)malloc(sizeof(int) * 10);//char *str = (char *)malloc(sizeof(char)*10);if (p == NULL){printf("malloc error\n");return -1;}char* tmp = p;// 记录malloc返回的地址值。用于free// 写数据到 malloc 空间。for (size_t i = 0; i < 10; i++){p[i] = i + 10;}// 读出malloc空间中的数据//for (size_t i = 0; i < 10; i++)//{//printf("%d ", *(p+i));//}for (size_t i = 0; i < 10; i++){printf("%d ", *p);p++;}// 释放申请的内存。free(tmp);p = NULL;system("pause");return EXIT_SUCCESS;}

8.4 二级指针malloc空间

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){int** p = malloc(sizeof(int*) * 3);// int **p ==> int *p[10]; ==> [ int *, int *, int * ]for (size_t i = 0; i < 3; i++){p[i] = malloc(sizeof(int) * 5);}// 使用空间 -- 写for (size_t i = 0; i < 3; i++){for (size_t j = 0; j < 5; j++){p[i][j] = i + j;}}// 使用空间 -- 读for (size_t i = 0; i < 3; i++){for (size_t j = 0; j < 5; j++){printf("%d ", *(*(p + i) + j));// p[i][j] == *(p+i)[j] == *(*(p+i)+j)}printf("\n");}// 释放空间时，应先释放内层空间。for (size_t i = 0; i < 3; i++){free(p[i]); //*(p+i)p[i] = NULL;}// 释放外层空间free(p);p = NULL;system("pause");return EXIT_SUCCESS;}

9. 文件

9.1 联合体和枚举

9.1.1 联合体

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include typedef union test {char ch;short sh;int a;}test_t;int main(void){test_t obj;obj.a = 0x87654321;printf("&obj= %p\n", &obj);printf("&obj.ch = %p\n", &obj.ch);printf("&obj.sh = %p\n", &obj.sh);printf("&obj.a= %p\n", &obj.a);printf("sizeof(test_t) = %u\n", sizeof(test_t));printf("a= 0x%x\n", obj.a);printf("sh = 0x%x\n", obj.sh);printf("ch = 0x%x\n", obj.ch);obj.ch = 0xFF;printf("a= 0x%x\n", obj.a);printf("sh = 0x%x\n", obj.sh);printf("ch = 0x%x\n", obj.ch);system("pause");return EXIT_SUCCESS;}enumcolor { red, green = -5, blue, black, pink = 18, yellow };

9.1.2 枚举

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include typedef union test {char ch;short sh;int a;}test_t;enumcolor { red, green = -5, blue, black, pink = 18, yellow };int main(void){int flg = 2;// ......if (flg == blue){printf("blue is 2\n");}else{printf("blue is not 2, blue = %d\n", blue);}printf("yellow = %d\n", yellow);system("pause");return EXIT_SUCCESS;}

9.2 系统文件

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){fclose(stdout);printf("hello file\n");system("pause");return EXIT_SUCCESS;}

9.3 文件的打开和关闭

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){FILE* fp = NULL;fp = fopen("test2.txt", "w");if (fp == NULL){perror("fopen error");//printf("fopen error\n");:xxxxxxxgetchar();return -1;}fclose(fp);printf("------------finish\n");system("pause");return EXIT_SUCCESS;}

9.4 fput和fget

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){char *filename = "test04.txt";FILE *fp = fopen(filename, "w");if (fp == NULL){perror("fopen error");return -1;}int ret = fputc('A', fp);printf("ret = %d\n", ret);fclose(fp);printf("---------------finish\n");system("pause");return EXIT_SUCCESS;}

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){char* buf = "abcdefghijklmnopqrstuvwxyz";char* filename = "test04.txt";int ret = 0;FILE* fp = fopen(filename, "w");if (fp == NULL){perror("fopen error");return -1;}int n = strlen(buf);for (size_t i = 0; i < n; i++){ret = fputc(buf[i], fp);if (ret == -1){perror("fputc eror");return -1;}}fclose(fp);system("pause");return EXIT_SUCCESS;}

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include void write_file(){FILE* fp = fopen("05test.txt", "w");if (fp == NULL){perror("fopen error");return;}fputc('a', fp);fputc('b', fp);fputc('c', fp);fputc('d', fp);fclose(fp);}void read_file(){char ch = 0;FILE* fp = fopen("05test.txt", "r");if (fp == NULL){perror("fopen error");return;}while (1){ch = fgetc(fp);// 读取一个字符if (ch == EOF){break;}printf("%d\n", ch);}fclose(fp);}int main(void){//write_file();read_file();system("pause");return EXIT_SUCCESS;}

9.5 feof

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include void read_file06(){char ch = 0;FILE* fp = fopen("06test.txt", "r");if (fp == NULL){perror("fopen error");return;}while (1){ch = fgetc(fp);if (feof(fp)){break;}printf("%d\n", ch);}fclose(fp);}void test_feof(){FILE* fp = fopen("06test.txt", "r");if (fp == NULL){perror("fopen error");return;}while (1){printf("没有到达文件结尾\n");fgetc(fp);// 一次读一个字符，读到字符直接丢弃。if (feof(fp)){break;}}fclose(fp);}void write_file06(){FILE* fp = fopen("06test.txt", "w");if (fp == NULL){perror("fopen error");return;}fputc('a', fp);fputc('b', fp);fputc(-1, fp);fputc('c', fp);fputc('d', fp);fputc('\n', fp);fclose(fp);}int main(void){write_file06();read_file06();test_feof();system("pause");return EXIT_SUCCESS;}

9.6 fgets和fputs

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){FILE* fp = fopen("test07.txt", "w");if (fp == NULL){perror("fopen error");return -1;}char buf[4096] = { 0 };while (1){fgets(buf, 4096, stdin);if (strcmp(buf, ":wq\n") == 0){break;}fputs(buf, fp);}fclose(fp);system("pause");return EXIT_SUCCESS;}

9.7 四则运算（文件版）

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include void write_file08(){FILE* fp = fopen("test08.txt", "w");if (fp == NULL){perror("fopen error");return;}fputs("10/2=\n", fp);fputs("10*3=\n", fp);fputs("4-2=\n", fp);fputs("10+2=\n", fp);fclose(fp);}int calc(char ch, int a, int b){switch (ch){case '/':return a / b;case '+':return a + b;case '-':return a - b;case '*':return a * b;default:break;}}void read_file08(){char buf[4096] = { 0 };char result[4096] = { 0 };char sum_res[4096] = { 0 };int a, b, ret;char ch;FILE* fp = fopen("test08.txt", "r");if (fp == NULL){perror("fopen error");return;}while (1){fgets(buf, 4096, fp);//buf = "10/2=\n\0";if (feof(fp)){break;}sscanf(buf, "%d%c%d=\n", &a, &ch, &b);// a：10， ch：'/' b: 2sprintf(result, "%d%c%d=%d\n", a, ch, b, calc(ch, a, b));// 10 / 2 = 5;strcat(sum_res, result);}fclose(fp);// 将 只有表达式没有结果的文件关闭。fp = fopen("test08.txt", "w");// 清空 只有表达式没有结果的文件if (fp == NULL){perror("fopen error");return;}fputs(sum_res, fp);// 将 既有表达式又有结果的字符串写到文件中。fclose(fp);}int main(void){write_file08();getchar();read_file08();system("pause");return EXIT_SUCCESS;}

9.8 sprintf和sscanf

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include void write_file(){FILE* fp = fopen("abc.c", "w");if (!fp)// fp == NULL{perror("fopen error");return -1;}fprintf(fp, "%d\n", 10);fprintf(fp, "%d\n", 8);fprintf(fp, "%d\n", 6);fclose(fp);}void read_file(){int a;FILE* fp = fopen("abc.c", "r");if (!fp)// fp == NULL{perror("fopen error");return -1;}fscanf(fp, "%d\n", &a);printf("%d\n", a);fscanf(fp, "%d\n", &a);printf("%d\n", a);fscanf(fp, "%d\n", &a);printf("%d\n", a);a = 0;fscanf(fp, "%d\n", &a);printf("%d\n", a);fclose(fp);}// fscanf 循环读文件void read_file2(){int a;FILE* fp = fopen("abc.c", "r");if (!fp)// fp == NULL{perror("fopen error");return -1;}while (1){fscanf(fp, "%d\n", &a);// 读printf("%d\n", a);if (feof(fp))// 真-- 文件结尾break;}fclose(fp);}// fgets 循环读文件void read_file3(){char buf[1024];FILE* fp = fopen("abc.c", "r");if (!fp)// fp == NULL{perror("fopen error");return -1;}while (1){memset(buf, 0, 1024);fgets(buf, 1024, fp);// 读 \nif (feof(fp))// 真-- 文件结尾break;printf("%d\n", buf[0]);}fclose(fp);}int main(void){FILE* fp = fopen("test0101.txt", "r");if (!fp)// fp == NULL{perror("fopen error");return -1;}int a;char ch;char str[10];int ret = fscanf(fp, "%d %c %s", &a, &ch, str);printf("ret = %d\n", ret);fclose(fp);system("pause");return EXIT_SUCCESS;}

9.9 文件版随机排序

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include void write_rand(){FILE *fp = fopen("test02.txt", "w");if (!fp)// fp == NULL{perror("fopen error");return -1;}srand(time(NULL)); // 随机数种子for (size_t i = 0; i < 10; i++){fprintf(fp, "%d\n", rand() % 100);// 将生成的随机数写入文件}fclose(fp);}void BubbleSort(int * src, int len){for (int i = 0; i < len - 1; i++){for (int j = 0; j < len - 1 - i; j++){if (src[j] > src[j + 1]){int temp = src[j];src[j] = src[j + 1];src[j + 1] = temp;}}}}void read_rand02(){int arr[10], i = 0;FILE *fp = fopen("test02.txt", "r");if (!fp)// fp == NULL{perror("fopen error");return -1;}while (1){fscanf(fp, "%d\n", &arr[i]);// 从文件中读取一个随机数，存入数组arri++;if (feof(fp))// 先存储，后判断，防止最后一个元素丢失break;}BubbleSort(arr, sizeof(arr)/sizeof(arr[0]));// 对读取到的乱序数组排序fclose(fp);// 关闭文件fp = fopen("test02.txt", "w");// 重新w方式打开文件， 清空原未排序文件。if (!fp)// fp == NULL{perror("fopen error");return -1;}for (size_t i = 0; i < 10; i++)fprintf(fp, "%d\n", arr[i]);// 写排好序的数组到文件fclose(fp);}int main(void){write_rand();getchar();read_rand02();system("pause");return EXIT_SUCCESS;}

9.10 结构化读取fwrite和fread

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include typedef struct student {int age;char name[10];int num;} stu_t;void write_struct(){stu_t stu[4] = {18, "afei", 10,20, "andy", 20,30, "lily", 30,16, "james", 40};FILE *fp = fopen("test03.txt", "w");if (!fp){perror("fopen error");return -1;}int ret = fwrite(&stu[0], 1, sizeof(stu_t) * 4, fp);if (ret == 0){perror("fwrite error");return -1;}printf("ret = %d\n", ret);fclose(fp);}// 一次读一个元素。void read_struct(){FILE *fp = fopen("test03.txt", "r");if (!fp){perror("fopen error");return -1;}stu_t s1;int ret = fread(&s1, 1, sizeof(stu_t), fp);printf("ret = %d\n", ret);printf("age = %d, name=%s, num = %d\n", s1.age, s1.name, s1.num);fclose(fp);}// 读所有元素void read_struct2(){FILE *fp = fopen("test03.txt", "r");if (!fp){perror("fopen error");return -1;}stu_t s1[10];// stu_t *s1 = malloc(sizeof(stu_t) * 1024);int i = 0;while (1){int ret = fread(&s1[i], 1, sizeof(stu_t), fp);//if (ret == 0)// 替代feof()函数来判断读到文件结尾。if (feof(fp)){break;}i++;printf("age = %d, name=%s, num = %d\n", s1[i].age, s1[i].name, s1[i].num);}fclose(fp);}int main(void){write_struct();read_struct2();system("pause");return EXIT_SUCCESS;}

9.11 大文件拷贝

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include void myfile_cp(){FILE *rfp = fopen("demo.avi", "rb");FILE *wfp = fopen("mycopy.avi", "wb");char buf[4096] = {0};int ret = 0;while (1){memset(buf, 0, sizeof(buf));ret = fread(buf, 1, sizeof(buf), rfp);if (ret == 0){break;}printf("ret = %d\n", ret);fwrite(buf, 1, ret, wfp);}fclose(wfp);fclose(rfp);}int main(void){myfile_cp();printf("---------------------finish\n");system("pause");return EXIT_SUCCESS;}

9.12 随机读取文件

9.12.1 fseek

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include typedef struct student {int age;char name[10];int num;} stu_t;int main(void){stu_t stu[4] = {18, "afei", 10,20, "andy", 20,30, "lily", 30,16, "james", 40};stu_t s1;FILE* fp = fopen("test05.txt", "wb+");if (!fp)// fp == NULL{perror("fopen error");return -1;}int ret = fwrite(&stu[0], 1, sizeof(stu), fp);// 以二进制形式写入，printf("ret = %d\n", ret);fseek(fp, sizeof(stu_t) * 2, SEEK_SET);// 从文件起始位置，向后偏移一个stu结构体ret = fread(&s1, 1, sizeof(s1), fp);printf("ret = %d\n", ret);printf("1 age= %d, name=%s, num=%d\n", s1.age, s1.name, s1.num);int len = ftell(fp); // 获取文件当前读写指针位置，到文件起始位置的偏移量。printf("len = %d\n", len);rewind(fp);// 将文件读写指针回卷到起始。ret = fread(&s1, 1, sizeof(s1), fp);printf("2 age= %d, name=%s, num=%d\n", s1.age, s1.name, s1.num);// 获取文件大小。fseek(fp, 0, SEEK_END);// 将文件读写指针放到文件结尾。len = ftell(fp);printf("文件大小为：%d\n", len);fclose(fp);system("pause");return EXIT_SUCCESS;}

9.12.2 改变指针位置

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main(void){FILE *fp = fopen("test0501.txt", "w+");// "r+"int ret = fputs("11111", fp);printf("ret 1 = %d\n", ret);// 0 表示成功。ret = fputs("22222", fp);printf("ret 2 = %d\n", ret);ret = fputs("33333", fp);printf("ret 3 = %d\n", ret);char buf[1024] = { 0 };//fseek(fp, 5 * 2, SEEK_SET);// 改变读写指针位置。rewind(fp); // 起始位置。char *ptr = fgets(buf, 1024, fp);if (ptr == NULL)printf("ptr == NULL \n");printf("fgets ptr = %s\n", ptr);printf("buf = %s\n", buf);fclose(fp);system("pause");return EXIT_SUCCESS;}

9.12.3 读取指针位置

#include #include #include int main(int argc, char *argv[]){FILE *fp = fopen("test1.txt", "r+");char buf[6] = { 0 };char *ptr = fgets(buf, 6, fp);printf("buf=%s, ptr=%s\n", ptr, buf);fseek(fp, 0, SEEK_CUR);int ret = fputs("AAAAA", fp);printf("ret = %d\n", ret);fclose(fp);system("pause");return 0;}

9.13 获取文件属性

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include #include #include /*FILE *fp = fopen("test05.txt", "r");fseek(fp, 0, SEEK_END);int len = ftell(fp);printf("文件大小：%d\n", len);fclose(fp);*/int main(void){struct stat buf;int ret = stat("test05.txt", &buf);// 传出参数：在函数调用结束时，充当函数返回值。printf("文件大小：%d\n", buf.st_size); // 不打开文件，获取文件大小。system("pause");return EXIT_SUCCESS;}

9.14 缓存区刷新

#define _CRT_SECURE_NO_WARNINGS#include #include #include #include #include int main0701(void){FILE *fp = fopen("test07.txt", "w+");if (!fp){perror("fopen error");return -1;}char m = 0;while (1) {scanf("%c", &m);if (m == ':'){break;}fputc(m, fp);fflush(fp);// 手动刷新文件缓冲到物理磁盘。}// 当文件关闭时，会自动刷新缓冲区。fclose(fp);system("pause");return EXIT_SUCCESS;}

C语言从入门到精通

文章目录

C语言

1.helloworld

1.1 pause

1.2 cls清屏

1.3 加法运算

1.4 hello

2 常量变量和数据类型

2.1 常量

2.2 变量

2.3 sizeof数据类型大小

2.4 无符号整型

2.5 字符类型

2.5.1 字符类型简介

2.5.2 字符类型运算

2.6 实数型

2.7 进制和转换

2.8 数据溢出

3. 运算符和分支循环语句

3.1 字符串输出

3.1.1 字符数组输出

3.1.2 字符数组格式化输出(%-15s)

3.1.2 字符输出 (putchar)

3.2 格式化输入

3.2.1 获取单个输入

3.2.2 获取多个输入

3.2.3 连续相同输入

3.2.4 字符数组输入

3.2.5 getchar获取字符输入

3.3 算数运算符

3.3.1 数学运算

3.3.2 自增运算（a++与++a）

3.4 逻辑运算

3.5 三目运算

3.5.1 三目运算使用

3.5.2 三目运算案例2

3.6 隐式转换和强制类型转换

3.6.1 隐式转换

3.6.2 强制类型转换

3.7 if 语句

3.7.1 if …else… 语句

3.7.2 else if语句

3.7.3 if else if else 语句

3.8 switch

3.9 while 循环

3.10 do while

3.10.1 do…whie语句

3.10.2 水仙花数问题

4. for循环和数组排序

4.1 for 循环

4.1.1 基础的for循环

4.1.2 省略的表达式1

4.1.3 省略表达式2

4.1.4 省略表达式123

4.1.5 多个表达式

4.2 猜数字游戏

4.3 模拟电子表

4.4 9*9乘法表

4.4.1 正序9*9乘法表

4.4.2 倒序9*9乘法表

4.5 continue

4.5.1 for 循环中continue

4.5.2 while循环中continue

4.6 goto语句

4.6.1 goto语句简介

4.6.2 循环语句中goto

4.7 数组

4.7.1 数组简介

4.7.2 数组大小与个数

4.7.3 数组初始化

4.8 数组逆序

4.9 冒泡排序

5. 二维数组、字符串、函数

5.1 二维数组

5.1.1 二维数组定义

5.1.2 二维数组练习

5.1.3 多维数组

5.2 字符数组和字符串

5.2.1 字符数组打印

**4.4 9*9乘法表**

**4.4.1 正序9*9乘法表**

**4.4.2 倒序9*9乘法表**

6.3 泛型指针(void )**

**6.4.2 const int *p**

**6.4.3 int const *p**

**6.4.4 int * const p**

**6.4.5 const int * const p**