use of static variables and functions

[justStarting]

So I must create a function that uses a static variable to keep track of a bank balance (it should be in a separate function but I can't even get this straightened out). I'm running into some issues and I think I might be using the static variable/function wrong. my overdraft is coming up properly but its factoring in the (-) negative amount when it should just be voiding that entry. Like I said, this should be in the form of two functions and one containing the bank balance, but I seem to have all the lines of code in that void function and my main function is just calling that function.. pretty sure that's not how it should go.

Thank you for any clarification.

#include <iostream>
#include <iomanip>


using namespace std;

int main()
{	
	cout << fixed << setprecision(2);
	char choice;
	static double balance;
	double cash;

	do
	{			
		cout << "Enter amount of transaction, positive for deposit, negative for withdrawal" << endl;
		cin >> cash;
		balance += cash;
			
			
		//if statment to prevent an overdraft
		if (balance >= 0)									
		cout << "Current Balance = " << balance << endl;
		else 
		cout << "Impermissible withdrawal, insufficient funds!" << endl;		
	
	cout << "Do you have more transactions? <Y or N>"; // runs another transaction when user enters "Y/y"
		cin >> choice;
	} while (choice == 'Y' || choice == 'y');
	
	cout << "Final Balance " << balance << endl;
	

	return 0;
}

/*
Enter amount of transaction, positive for depostit, negative for withdrawal
50
Current Balance = 50.00
Do you have more transactions? <Y or N>y
Enter amount of transaction, positive for deposit, negative for withdrawal
50
Current Balance = 100.00
Do you have more transactions? <Y or N>y
Enter amount of transaction, positive for deposit, negative for withdrawal
-105
Impermissible withdrawal, insufficient funds!
Do you have more transactions? <Y or N>y
Enter amount of transaction, positive for deposit, negative for withdrawal
50
Current Balance = 45.00
Do you have more transactions? <Y or N>n
Final Balance 45.00
Press any key to continue . . .
*/

[jonnin]

static in main does not do much :)

lets stop here and have a little study on static:

int foo()
{
    static int x = 0;
    return x++;
}

int main()
{
    for(int z = 0; z < 10; z++)
    cout << foo() << endl; 
}

Run this.


ok, now, what you just saw was that x in foo is keeping its value, even though the function exited. Now remove the static keyword, and you get a totally different behavior: x forgets its value every time it runs and it goes back to zero every time. Static values inside functions exist for the life of the PROGRAM not the life of the function.

Given that, what you are asked to do is write a function that uses this capability to keep track of a value. Can you do it now?

[tpb]

One potential use of static in main is to not allocate a large object on the stack:

int main() {
    static char big[100000000]; // 100MB char array
    //...
}

[justStarting]

Thanks for the responses, I think I have it now.