struct Point {float x;float y;
} point;                      //等价于: struct  Point  point;

struct  {float x;float y;
} point;                      //等价于:  struct  Point  point;

#include <stdio.h>struct {                                                  unsigned mode:8;          //bit[0,7]:模式选择unsigned en:1;            //bit[8]   :使能选择unsigned reserved:1;      //bit[9]    :保留reserved  (也可以写成unsigned reserved:1;)unsigned clk_select:4;    //bit[10,13]:时钟选择unsigned ch_select:3;     //bit[14,15]:通道选择
}reg11;            //定义一个reg11变量,不声明结构体的好处在于确保变量唯一性int main()
{      reg11.en =1;                     //bit8=1 --> 256printf("reg11=%d\n",reg11);         //打印 256
reg11.mode =50;printf("reg11=%d\n",reg11);         //打印 256+50return 0;
}

#include <stdio.h>
struct {                                                  unsigned mode:8;          //bit[0,7]:模式选择unsigned en:1;            //bit[8]   :使能选择unsigned reserved:1;      //bit[9]    :保留reserved(也可以写成unsigned reserved:1;)unsigned clk_select:4;    //bit[10,13]:时钟选择unsigned ch_select:3;     //bit[14,15]:通道选择
}reg11;     //定义一个reg11变量,不声明结构体的好处在于确保变量唯一性int main()
{     reg11.en =1;                     //bit8=1 --> 256printf("1st:reg11=%d\n",reg11);  //打印 256reg11.en =5;                     //5(b'101) 保留低1位: b'1printf("2st:reg11=%d\n",reg11);  //打印 256
reg11.en =6;                     //5(b'110) 保留低1位: b'0printf("3st:reg11=%d\n",reg11);  //打印 0return 0;
}

#include <stdio.h>struct {unsigned a:4;unsigned b:2;unsigned c:1;
}reg1;　　　　　　　　//位域总长度只有7位struct reg{unsigned a:4;unsigned b:2;unsigned c:32;
}reg2;int main()
{      printf("%d\n",sizeof(reg1));printf("%d\n",sizeof(reg2));return 0;
}

#include <stdio.h>typedef union{
unsigned char val;struct {                                                  unsigned a:4; unsigned b:1; unsigned c:2;unsigned d:1;}bit;       }reg11;             //使用typedef ,告诉编译器,reg11是个声明类型int main()
{      reg11 reg;printf("sizeof=%d\n",sizeof(reg.val));reg.val=0;reg.bit.b = 1;            //bit[4]=1printf("val = %d\n",reg.val);return 0;
}

typedef struct {unsigned OVL     :6;unsigned OVOLCN :2;
}rg11;
rg11 reg = {57,1};            //初始化reg变量  OVL=57   OVOLCN=1