IP与子网掩码的关系图文详解

#include<stdio.h>
#define uchar unsigned char
#define uint unsigned int
uchar bin1num(uchar num);
void main() {
	uchar IP[] = {192,168,1,53};	//IP地址
	uchar SubnetMask[] = {255,255,255,224};	//子网掩码
	//网络类型和默认子网掩码缩写
	uchar DefaultSubnetMaskAbbr;
	if(IP[0]<224) DefaultSubnetMaskAbbr = 24;	//C类地址
	if(IP[0]<192) DefaultSubnetMaskAbbr = 16;	//B类地址
	if(IP[0]<128) DefaultSubnetMaskAbbr = 8;	//A类地址
	//实际子网掩码缩写：二进制中1的个数
	uchar SubnetMaskAbbr = bin1num(SubnetMask[0])+bin1num(SubnetMask[1])+bin1num(SubnetMask[2])+bin1num(SubnetMask[3]);
	//网络地址：IP & 子网掩码
	uchar Network[] = {IP[0] & SubnetMask[0], IP[1] & SubnetMask[1], IP[2] & SubnetMask[2], IP[3] & SubnetMask[3]};
	//广播地址：(~子网掩码)|网络地址
	uchar Broadcast[] = {(~SubnetMask[0])|Network[0], (~SubnetMask[1])|Network[1], (~SubnetMask[2])|Network[2], (~SubnetMask[3])|Network[3]};
	//子网数：2^(实际子网掩码缩写-默认子网掩码缩写)
	uint SubnetNum = 1;
	for(int i=0; i<SubnetMaskAbbr-DefaultSubnetMaskAbbr; i++) {
		SubnetNum *=2;
	}
	//最大主机数：2^(32-子网掩码缩写)
	uint HostNum = 1;
	for(int i=0; i<32-SubnetMaskAbbr; i++) {
		HostNum *=2;
	}
	/*打印结果*/
	printf("ip地址：%d.%d.%d.%d\n", IP[0], IP[1], IP[2], IP[3]);
	printf("子网掩码：%d.%d.%d.%d\n", SubnetMask[0], SubnetMask[1], SubnetMask[2], SubnetMask[3]);
	if(DefaultSubnetMaskAbbr==8) printf("网络类型：A类\n");
	if(DefaultSubnetMaskAbbr==16) printf("网络类型：B类\n");
	if(DefaultSubnetMaskAbbr==24) printf("网络类型：C类\n");
	printf("子网掩码缩写：%d\n", SubnetMaskAbbr);
	printf("网络地址：%d.%d.%d.%d\n", Network[0], Network[1], Network[2], Network[3]);
	printf("广播地址：%d.%d.%d.%d\n", Broadcast[0], Broadcast[1], Broadcast[2], Broadcast[3]);
	printf("子网数：%d\n", SubnetNum);
	printf("最大主机数：%d\n", HostNum);
	printf("可用主机数：%d\n", HostNum-2);
}
//计算8位二进制数1的个数(1必须从第一位开始，每个1必须相邻)
uchar bin1num(uchar num) {
	uchar Divisor[] = {128,64,32,16,8,4,2,1};	//除数(8位)
	uchar Remainder = num;	 //余数
	uchar ret;	//结果
	for(ret=0; ret<10; ret++) {
		if(Remainder>0) Remainder = Remainder%Divisor[ret];
		else break;
	}
	return ret;
}