help me how to begin please...

help me how to begin to recode my ATM program, that need to be in a system... I don't how to begin.. ATM system must register user, and keep username and password... anyone? give me an idea please... this is my project deadline is on tomorrow, so i work to this as soon as I reach the requirements...

heres my ATM program, not in a system yet..

Code:

#include <stdio.h>
#include <conio.h>
double amount=10000.00;
double dep(double y){
double newaccount;
newaccount=amount+y;
return newaccount;}
double with(double x){
double newaccount;
if(x>=4001)
printf("The largest amount you can withdraw is 4000");
else if(x>=10001)
printf("You exceed to your bank savings");
else
newaccount=amount-x;
printf("%lf",newaccount);
return 0;}


void main()
{
int i=0;
double j;
clrscr();
printf("\n*******MENU*********\n");
printf("1.Balance Enquiry\n");
printf("2.Deposit\n");
printf("3.Withdraw\n");
printf("4.Exit\n");
printf("Select an item from the menu: ");
scanf("%d",&i);
while(i<4)
{
switch(i)
{
case 1:printf("This is your balance amount: %f",amount);
break;
case 2:printf("How much would you like to withdraw?");
scanf("%lf",&j);

amount = with(j);
j=0;
printf("This is your balance amount: %f",amount);
break;
case 3:printf("How much amount do want to withdraw?\n");
scanf("%lf",&j);
amount = amount-j;
j=0;
printf("This is your balance amount: %f",amount);
break;
}
printf("\n*********MENU*********...\n");
printf("1.Balance Enquiry\n");
printf("2.Deposit\n");
printf("3.Withdraw\n");
printf("4.Exit\n");
printf("If you are a first time user please deposit some amount for balance enq uiry.\n");
printf("Select an item from the menu: ");
scanf("%d",&i);
}
getch();
}

thank you... i really need help right now, because i was abandoned by my group mates, and they transfer to other section.. so help me i'm begging...
thanks you so much...

A quick search pointed out to me that it has been suggested to you at least 3 times already:
- not to use void main
- do proper indentation
but it does not appear to be registering.

thanks sir heras..

or if someone have already that kind of program.. share your blessings to me please, i don't know what to do anymore.. i'm just expecting and hoping that their's a ghost besides me and he will teach me how to work to it... i really hoping...

sorry for asking a unforgivable favor... and don't judge, I know that I'm idiot when it comes to this, I can't really understand everything about programming, even I read some of the tutorials many times already.. i can't make my own logic, i think this field is not belong to me =(

I like programming but programming doesn't like me i think ^^

i don't know what to do anymore..

Do 3 things
1. read FAQ and change main to int main(void)
2. indent your code properlyt - so it will be readable by people going to answer your questions
3. Explain what output is expected and what output you are receiving