C Program for IP Addressing: Subnetting

#include<stdio.h>
#include<conio.h>
#include<stdlib.h>
void inputIP();
void classA();
void classB();
void classC();
int octet1, octet2, octet3, octet4;
int networks, address;
//networks- number of networks
//address- number of addresses in each network
int main() {
    char class_input;
    clrscr();
    printf("\nEnter class: ");
    scanf("%c", &class_input);
    printf("\nEnter starting IP Address: ");
    inputIP();
    printf("\nEnter number of networks: ");
    scanf("%d", &networks);
    printf("\nEnter number of address in each network: ");
    scanf("%d", &address);
    switch(class_input)  {
    case 'a':
    case 'A':
        if(octet1<0 || octet1>127)     printf("\nInvalid IP");
        else     classA();
        break;
    case 'b':
    case 'B':
        if(octet1<128 && octet1>191)     printf("\nInvalid IP");
        else     classB();
        break;
    case 'c':
    case 'C':
        if(octet1<192 && octet1>223)     printf("\nInvalid IP");
        else     classC();
        break;
    default:
        printf("\nInvalid Class");
    }
    getch();
    return 0;
}
//---- INPUT STARTING IP ADDRESS ----
void inputIP() {
    printf("\n\t1st Octet: ");
    scanf("%d", &octet1);
    printf("\n\t2nd Octet: ");
    scanf("%d", &octet2);
    printf("\n\t3rd Octet: ");
    scanf("%d", &octet3);
    printf("\n\t4th Octet: ");
    scanf("%d", &octet4);
    printf("\nThe IP Address entered is %d.%d.%d.%d", octet1, octet2, octet3, octet4);
}
//---- Class A ----
void classA() {
    int i;
    printf("\nNetwork\tStarting Address\tEnding Address\n");
    for(i=0; i<networks; i++)  {
        printf("   %d\t", i+1);
        printf("  %d.%d.%d.%d\t", octet1+i,octet2, octet3, octet4);
        printf("         %d.%d.%d.%d",octet1+i, octet2, octet3, octet4+address-1);
        printf("\n");
    }
}
//---- Class B ----
void classB() {
    int i;
    printf("\nNetwork\tStarting Address\tEnding Address\n");
    for(i=0; i<networks; i++)  {
        printf("   %d\t", i+1);
        printf("  %d.%d.%d.%d\t", octet1,octet2+i, octet3, octet4);
        printf("         %d.%d.%d.%d",octet1, octet2+i, octet3, octet4+address-1);
        printf("\n");
    }
}
//--- Class C ---
void classC() {
    int i;
    printf("\nNetwork\tStarting Address\tEnding Address\n");
    for(i=0; i<networks; i++)  {
        printf("   %d\t", i+1);
        printf("  %d.%d.%d.%d\t", octet1,octet2, octet3+i, octet4);
        printf("         %d.%d.%d.%d",octet1, octet2, octet3+i, octet4+address-1);
        printf("\n");
    }
}