c位域操作

 

#include <stdio.h>
int main()
{
    struct fields
    {
        unsigned short a:7;
        unsigned short b:5;
        unsigned char c:4;
        
    }fs;

    fs.a = 0x8F;
    fs.b = 0x1A;
    fs.c = 0x19;

    printf("%#x, %#x, %#x \n",fs.a, fs.b, fs.c);
    
}
用 gcc -g -o bitfield bitfield.c 编译并运行，结果为

[root@localhost]# ./bitfield                   
0xf, 0x1a, 0x9

我的理解：a占用0x8F的4位，b占用0x1A的5位，c占用0x19的4位。