C语言结构体,枚举,联合体详解

// 创建结构体
struct student
{
  char *name;  // 学生名字
  int num;     // 学生学号
  int age;     // 学生年龄
};

struct tag{
	成员变量...
}variable;

struct
{
	char name[100];
	int age;
}s1;//s1相当于对这个结构体声明了一个变量，可以在程序中直接调用

struct person
{
	char name[100];
	int age;
};

struct person p1,p2[5],*p3

typedef struct 
{
	char name[100];
	int age;
} person;

//用新定义的person类型定义变量
person p1,p2[5],*p3

struct B;				//需先对结构体B进行声明，不然声明A时编译无法通过
struct A
{
	struct B *partner;
	//other members;
};
struct B
{
	struct A *partner;
	//other members;
};

#include <stdio.h> 
struct persons {
    char name[100];
    int age;
}person = {"chuhe",18};
int main()
{
    printf("%s,%d", person.name, person.age);
    return 0;
}

#include <stdio.h> 
typedef struct persons {
    char name[100];    
    int age;
}persons;
int main()
{
    struct persons p = { "chuhe",18 };
    printf("%s,%d\n", p.name, p.age);
    persons* p1 = &p;//定义结构体指针
    printf("%s,%d\n", p1->name, p1->age);
    return 0;
}

enum 枚举名{元素1,元素2};

#define MON  1
#define TUE  2
#define WED  3
#define THU  4
#define FRI  5
#define SAT  6
#define SUN  7

enum DAY{MON=1,TUE,WED, THU, FRI, SAT, SUN};

enum DAY{MON=1,TUE,WED,THU,FRI};
enum DAY day;
enum DAY{MON=1,TUE,WED,THU,FRI}day;//也可以在定义枚举类型时一起定义
enum{MON=1, TUE, WED, THU, FRI, SAT, SUN}day;//可以省略枚举名称

#include <stdio.h>
enum DAY
{
      MON=1, TUE, WED, THU, FRI, SAT, SUN
};
int main()
{
    enum DAY day;
    day = WED;
    printf("%d",day);
    return 0;
}

#include <stdio.h>
#include <stdlib.h>
int main(){
    enum color { red=1, green, blue };
    enum  color favorite_color;
    printf("请输入你喜欢的颜色: (1. red, 2. green, 3. blue): ");
    scanf("%u", &favorite_color);
    switch (favorite_color){
    case red:
        printf("你喜欢的颜色是红色");
        break;
    case green:
        printf("你喜欢的颜色是绿色");
        break;
    case blue:
        printf("你喜欢的颜色是蓝色");
        break;
    default:
        printf("你没有选择你喜欢的颜色");
    }
    return 0;
}

union 共用体名{
    成员列表
};

union data{
    int n;
    char ch;
    double f;
};
union data a, b, c;

#include <stdio.h>
union data{
    int n;
    char ch;
    short m;
};
int main(){
    union data a;
    printf("%d, %d\n", sizeof(a), sizeof(union data) );
    a.n = 0x40;
    printf("%X, %c, %hX\n", a.n, a.ch, a.m);
    a.ch = '9';
    printf("%X, %c, %hX\n", a.n, a.ch, a.m);
    a.m = 0x2059;
    printf("%X, %c, %hX\n", a.n, a.ch, a.m);
    a.n = 0x3E25AD54;
    printf("%X, %c, %hX\n", a.n, a.ch, a.m);
    return 0;
}