Loop Issue

[shana898]

I need month #1's balance to be zero, but when I run the program, it is 100...Any suggestions?

Here is my code:

#include <iostream>

using namespace std;

int main()
{
	int down_payment, month, cnum;
	
	double  balance, payment, interest, shortage, total_interest;
	
	cout << "How much is your down payment for your car? ";
	cin >> down_payment;
	
	month = 1;
	balance = 0 ;
	total_interest = 0; 
	payment = 100;
	
		
	while (balance<=down_payment)
	{
		interest = balance * .001;
		balance = balance + payment + interest ;
		shortage = down_payment - balance;
		total_interest += interest;
		
		if (balance + payment >= down_payment)
		{
			payment = down_payment - balance ;
		}

		cout << "\nMONTH: \tBALANCE: \tPAYMENT: \tINTEREST: \tSHORTAGE:" ;
		cout << "\n" << month << "\t" << balance << "\t\t" << payment << "\t\t" << interest << "\t\t" << shortage ;
		month ++ ;
	}
	
	cout << "\nTotal number of months needed: " << month ;
	cout << "\nTotal amount of interest earned: " << total_interest ;
	
	cin >> cnum;

   return 0;
}

[Mats]

balance = balance + payment + interest ;

Payment = 100.

[shana898]

thats the thing. Every month the payment is 100, starting from the first month. but the balance of the first month is zero.

how do i get the balance of the first month to be zero and the rest of the months to be "balance = balance + payment + interest" ? thanks

[slambert]

Why not just initialize payment @ 0? And you should probably use a for loop not a while loop...
http://www.cplusplus.com/doc/tutorial/control/
ex:

/* I would initialize them all @ 0...
balance=0;
payment=0;
total_interest=0;
month=0;
*/

 for(months=0;balance<=downpayment;months++) //for(initializer;condition;increment)statement;
{ //Since you calculate your payment with the if statement you can initialize payment @ 0...
                interest = balance * .001; //You didn't initialize interest, I don't know if that's what you want...
		balance = balance + payment + interest ;
		shortage = down_payment - balance;
		total_interest += interest;
		
		if (balance + payment >= down_payment)
		{
			payment = down_payment - balance ;
		}
                else payment=100; // here's where you could put your 100...

		cout << "\nMONTH: \tBALANCE: \tPAYMENT: \tINTEREST: \tSHORTAGE:" ;
		cout << "\n" << month << "\t" << balance << "\t\t" << payment << "\t\t" << interest << "\t\t" << shortage ;
		// you can get rid of: month ++ ;
	}

Also what is with cnum? Why input with no output?
Anyways, I probably missed stuff but you get the general idea.

Sean

[MikeyBoy]

how do i get the balance of the first month to be zero and the rest of the months to be "balance = balance + payment + interest" ? thanks

You need to rethink the logic of your operations, so that your reporting of the first month's balance happens before it's adjusted for the first payment.