ATM program in C

/*Note Pin code is 1234*/

#include<stdio.h>

#include<conio.h>

void main(void)

{

            unsigned long amount=1000,deposit,withdr​aw;

            int choice,pin=0,k=0;

            char another='y';

            while(pin!=1234)

            {

                        clrscr();

                        gotoxy(30,25);

                        printf("Enter pin:");

                        scanf("%d",&pin);

            }

            clrscr();

            do

            {

                        printf("********Welcome to ATM Service**************\n");

                        printf("1. Check Balance\n");

                        printf("2. Withdraw Cash\n");

                        printf("3. Deposit Cash\n");

                        printf("4. Quit\n");

                        printf("******************​**************************​*\n\n");

                        printf("Enter your choice: ");

                        scanf("%d",&choice);

                        switch(choice)

                        {

                                    case 1:

                                                printf("\nYour Balance is Rs : %lu ",amount);

                                    break;

                                    case 2:

                                                printf("\nEnter the amount to withdraw: ");

                                                scanf("%lu",&withdraw);

                                                if(withdraw%100!=0)

                                                {

                                                            printf("\nPlease enter amount in multiples of 100");

                                                } else if(withdraw>(amount-500)) {

                                                            printf("\nInsufficient Funds");

                                                } else {

                                                            amount=amount-withdraw;

                                                            printf("\n\nPlease collect cash");

                                                            printf("\nYour balance is %lu",amount);

                                                }

                                    break;

                                    case 3:

                                                printf("\nEnter amount to deposit");

                                                scanf("%lu",&deposit);

                                                amount=amount+deposit;

                                                printf("Your balance is %lu",amount);

                                    break;

                                    case 4:

                                                printf("\nThank you for using ATM");

                                    break;

                                    default:

                                                printf("\nInvalid Choice");

                        }

                        printf("\n\n\nDo you want another transaction?(y/n): ");

                        fflush(stdin);

                        scanf("%c",&another);

                                    if(another=='n'||another==​'N')

                                                k=1;

            }

            while(!k);

            printf("\n\nHave a nice day");

            getch();

}