// C program to determine Class, Network ID, Host ID, Broadcast Id and Default Mask 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, Broadcast Id and Default Mask 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: %s\n", network);
        printf("Host ID: %s", host);
        printf("Default subnet mask: 255.0.0.0\n");
        printf("Broadcast ID:%s.255.255.255\n",network);
    }
    // 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", host);
        printf("Default subnet mask is 255.255.0.0\n");
        printf("Broadcast ID:%s.255.255\n",network);
    }
    // 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", host);
        printf("Default subnet mask is 255.255.255.0\n");
        printf("Broadcast ID:%s.255\n",network);
    }
    // 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");
}
//main function
int main()
{
    char str[20];
    printf("Please enter the IPV4 address: ");
    fgets(str,20,stdin);
    char ipClass = findClass(str);
    printf("Given IP address belongs to Class %c\n", ipClass);
    separate(str, ipClass);
    return 0;
}