I've searched for this a little, but I have not gotten a particularly straight answer. In C (and I guess C++), how do you determine what comes after the % when using printf?. For example:

double radius = 1.0;
double area = 0.0;
area = calculateArea(radius);
printf("%10.1f     %10.2\n", radius, area);

I took this example straight from a book that I have on the C language. This does not make sense to me at all. Where do you come up with 10.1f and 10.2f?