Assignment #1 Problem

I was going over the io_displayflag function stuff located here and I noticed a problem. First of all, it didn't specify which value we were supposed to return after it's done. Secondly, and this is more confusing, is that we cannot alter the contents of the format char. array, since it was designated as being const. This conflicts with the requirement that we're supposed to replace format[1] with either a space (' ') or a check (I'm using 'X' here), since const stuff can't be modified. I'm stumped here and I can't think of what to do. Maybe the arguements should be changed. If anyone has any thoughts on the matter, I'll all ears.