LogFAQs > #910494013

first off, you're using "while" incorrectly in main. You should be using "if" instead

if (n >= 0)
{
if (Prime(n) == 0)
cout << n << " is a prime number.";
else
cout << n << " is not a prime number.";
}
return 0;

'While' is meant to loop code and will repeat as long as the condition is met. 'if' will only go through once, which is what you're going for here I imagine.

If you want to loop through every number up until 12, you would have to use a 'for' loop in your main function.

int main()
{
int n;

cout << "Calculate every number up until: ";
cin >> n;

for (int i = 0; i < n; i++)
{
if (Prime(i) == 0)
cout << i << " is a prime number.\n";
else
cout << i << " is not a prime number.\n";
}
return 0;
}

Also, a little tip, to do line ends you can type \n in the middle of the string. That makes the output much easier to read. You can also use endl
http://www.cplusplus.com/forum/beginner/2138/