1、联合体的特点和大小

union是共用一个内存首地址，联合体中每个成员的地址都相同,等于联合体变量的首地址
联合体的大小足够容纳最宽的成员,大小能被其包含的所有基本数据类型的大小所整除

 

 

 

 

2、测试Demo

 

#include <stdio.h>union var 
{long int a;int b;
};union size
{int a;double b;char c[11];
};int main()
{union var v;v.a =  3.14;printf("v.b is %d\n", v.b);v.b = 6;printf("v.a is %ld the address is %p\n", v.a, &v.a);printf("v.b is %d the address is %p\n", v.b, &v.b);union size union_first;union size union_second;union size union_third;//大小足够容纳最宽的成员,大小能被其包含的所有基本数据类型的大小所整除printf("the sizeof union_first is %d\n", sizeof(union_first));printf("the sizeof union_second is %d\n", sizeof(union_second));printf("the sizeof union_third is %d\n", sizeof(union_third));printf("sizeof(long int) is %d\n", sizeof(long int));printf("the sizeof