C语言及程序设计进阶例程-30 联合体及其应用

贺老师教学链接 C语言及程序设计进阶 本课讲解

联合体的概念

#include <stdio.h>union un{int i;short int si[2];char c[4];};int main(){union un x;x.c[0]='A';x.c[1]='B';x.c[2]='C';x.c[3]='D';printf("%c, %c, %c, %c\n", x.c[0], x.c[1], x.c[2], x.c[3]);printf("%d, %d\n", x.si[0], x.si[1]);printf("%d\n", x.i);return 0;}

应用：IP的表示

#include <stdio.h>union IP{unsigned char part[4];unsigned int address;};void copyIp(union IP *a, int n[]){int i;for(i=0; i<4; i++)a->part[i]=n[i];return;}int main(){union IP ip1, ip2;int nums[4]= {202,194,116,97};copyIp(&ip1, nums);printf("ip1: %d.%d.%d.%d\n", ip1.part[0], ip1.part[1], ip1.part[2], ip1.part[3]);printf("ip1: %d\n", ip1.address);ip2.address=234567;printf("ip2: %d.%d.%d.%d\n", ip2.part[0], ip2.part[1], ip2.part[2], ip2.part[3]);printf("ip2: %d\n", ip2.address);if(ip1.address == ip2.address)printf("same ip.\n");elseprintf("not same ip.\n");return 0;}