// C program to determine class, Network
// and Host ID of an IPv4 address
#include<stdio.h>
#include<string.h>
// Function to find out the Class
char findClass(char str[])
// storing first octet in arr[] variable
char arr[4];
int i = 0;
while (str[i] != '.')
arr[i] = str[i];
i++;
i--;
// converting str[] variable into number for
// comparison
int ip = 0, j = 1;
while (i >= 0)
ip = ip + (str[i] - '0') * j;
j = j * 10;
i--;
// Class A
if (ip >=1 && ip <= 126)
return 'A';
// Class B
else if (ip >= 128 && ip <= 191)
return 'B';
// Class C
else if (ip >= 192 && ip <= 223)
return 'C';
// Class D
else if (ip >= 224 && ip <= 239)
return 'D';
// Class E
else
return 'E';
// Function to separate Network ID as well as
// Host ID and print them
void separate(char str[], char ipClass)
// Initializing network and host array to NULL
char network[12], host[12];
for (int k = 0; k < 12; k++)
network[k] = host[k] = '\0';
// for class A, only first octet is Network ID
// and rest are Host ID
if (ipClass == 'A')
int i = 0, j = 0;
while (str[j] != '.')
network[i++] = str[j++];
i = 0;
j++;
while (str[j] != '\0')
host[i++] = str[j++];
printf("Network ID is %s\n", network);
printf("Host ID is %s\n", host);
// for class B, first two octet are Network ID
// and rest are Host ID
else if (ipClass == 'B')
int i = 0, j = 0, dotCount = 0;
// storing in network[] up to 2nd dot
// dotCount keeps track of number of
// dots or octets passed
while (dotCount < 2)
network[i++] = str[j++];
if (str[j] == '.')
dotCount++;
}
i = 0;
j++;
while (str[j] != '\0')
host[i++] = str[j++];
printf("Network ID is %s\n", network);
printf("Host ID is %s\n", host);
// for class C, first three octet are Network ID
// and rest are Host ID
else if (ipClass == 'C')
int i = 0, j = 0, dotCount = 0;
// storing in network[] up to 3rd dot
// dotCount keeps track of number of
// dots or octets passed
while (dotCount < 3)
network[i++] = str[j++];
if (str[j] == '.')
dotCount++;
i = 0;
j++;
while (str[j] != '\0')
host[i++] = str[j++];
printf("Network ID is %s\n", network);
printf("Host ID is %s\n", host);
// Class D and E are not divided in Network
// and Host ID
else
printf("In this Class, IP address is not"
" divided into Network and Host ID\n");
// Driver function is to test above function
int main()
char str[] = "192.226.12.11";
char ipClass = findClass(str);
printf("Given IP address belongs to Class %c\n",
ipClass);
separate(str, ipClass);
return 0;
