联合体应用：验证当前主机的大小端（字节序）
//验证当前主机的大小端
#include <stdio.h>
union MyData
{
unsigned int data;
struct
{
unsigned char byte0;
unsigned char byte1;
unsigned char byte2;
unsigned char byte3;
}byte;
};
int main()
{
union MyData num;
num.data = 0x12345678;
if (0x78 == num.byte.byte0)
{
printf("小端字节序\n");
}
else if (0x78 == num.byte.byte3)
{
printf("大端字节序\n");
}
return 0;
}
枚举
枚举（Enumeration）是一种在编程语言中表示一组具名常量的数据类型。
//使用枚举包含一周的七个值
#include <stdio.h>
// 定义一个枚举类型
enum Weekday
{
MONDAY,
TUESDAY,
WEDNESDAY,
THURSDAY,
FRIDAY,
SATURDAY,
SUNDAY
};
int main()
{
// 定义枚举变量
enum Weekday today;
// 设置枚举变量的值
today = WEDNESDAY;
// 使用 switch 语句根据枚举变量的值进行处理
switch (today)
{
case MONDAY:
printf("Today is Monday.\n");
break;
case TUESDAY:
printf("Today is Tuesday.\n");
break;
case WEDNESDAY:
printf("Today is Wednesday.\n");
break;
case THURSDAY:
printf("Today is Thursday.\n");
break;
case FRIDAY:
printf("Today is Friday.\n");
break;
case SATURDAY:
printf("Today is Saturday.\n");
break;
case SUNDAY:
printf("Today is Sunday.\n");
break;
default:
printf("Invalid day.\n");
}
return 0;
}
枚举常常用于定义一组相关的离散值，比如颜色、星期几、月份等。
