Numbers Drifting

[joelsjet]

Hi Guys
Heres My Code It's really Simple I'm very very new so hope you all can help

#include "stdafx.h"
#include <iostream>

int main()
{
    using namespace std;
	cout << "Welcome To Joels Bakehouse" << endl;
	cout << "White Loaves are $3.20 Each" << endl;
    cout << "How many loaves of bread would you like:" << endl;
	int nWhiteLoavesAmount;
	cin >> nWhiteLoavesAmount;
	float fMoney = 3.20;
	float fMoney2 = fMoney*nWhiteLoavesAmount;
	int nDollars =fMoney2;
	int nCents =(fMoney2-nDollars)*100;	
	cout << "That comes to: " << nDollars << " Dollars and " << nCents << " Cents" << endl;
	bool Eftpos;
	cout << "To Pay By Cash Type 0" << endl;
	cout << "To Pay By Eftpos Type 1" << endl;
	cin >> Eftpos;
if (Eftpos)
	cout << ".... Transaction Confirmed. Thank you for your buisness!" << endl;
else
{
	cout << "Okay, How Much Cash Do You Have?" << endl;
	float Cash;
	cin >> Cash;
	cout << "Thats" << Cash-fMoney2 << " Change" << endl;
	cout << "Thank you for your buisness!" << endl;
}
	return 0;
}

The Problem is if you ask for say
7 loaves of bread you end up with $22 and 39 Cents not 40 Cents ???
I Think Ive read about this but i cant work it out

Thanks for your help
Joel:)

[Zhuge]

I would suspect floating point approximation errors here. Why not just store all monetary values as integers representing the number of cents?

[Moschops]

Floating point numbers cannot represent every decimal exactly (in fact, there are infinitely many more that it cannot represent than it can represent).

http://floating-point-gui.de/

Don't use float for money (or anything where you need exact calculations). Commonly, people use integers values for money.

[joelsjet]

Okay Used Double instead of float fixed it completly

Thanks All
Joel

[Moschops]

A double IS a floating point number. A double may have more precision than a regular float (the standard doesn't dictate that it will). Don't use floating point numbers when dealing with money. Use int.