使用union在成员之间共享内存

结构体为每个成员保留单独的内存段，union为其最大成员保留单个内存空间。使用关键字union创建联合体。
以下代码为电话簿创建联合体定义。

union phoneBook { 
   char *name; 
   char *number; 
   char *address; 
};

通过点(.)运算符访问联合体成员。

#include <stdio.h> 
union phoneBook { 
   char *name; 
   char *number; 
   char *address; 
}; 

struct magazine { 
   char *name; 
   char *author; 
   int isbn; 
}; 

int main()
{ 
   union phoneBook aBook; 
   struct magazine aMagazine; 
   printf("\nUnion Details\n"); 
   printf("Address for aBook.name: %p\n", &aBook.name); 
   printf("Address for aBook.number: %p\n", &aBook.number); 
   printf("Address for aBook.address: %p\n", &aBook.address); 
   printf("\nStructure Details\n"); 
   printf("Address for aMagazine.name: %p\n", &aMagazine.name); 
   printf("Address for aMagazine.author: %p\n", &aMagazine.author); 
   printf("Address for aMagazine.isbn: %p\n", &aMagazine.isbn); 
} //end main