If you consider using a different starting value you can more clearly see the difference:
int number = 10;
while (number<10)
{
cout << number << endl;
number++
}
// no output
In the first example the condition immeditately fails, so the loop won't execute. However, because the condition isn't tested until after the loop code in the 2nd example, you'll get a single iteration.
int number = 10;
do
{
cout << number << endl;
number++
}
while (number<10);
// output: 10
