If I’m understanding correctly, a BOOL variable is for storing true/false values. You could use a int instead, since in C, 0 is equal to false, and 1, 2, 3, 4, 5, etc… (even -1 I think) is equal to true. I’m not sure what would happen if you tried to use a float, though I don’t suspect it’s a very good idea. If you know the expression could only have true or false results (like x > y), then using a BOOL would make for the clearest code, and reduce the chances of introducing a logical error.
e: I’ll defer to the author – great book Aaron!
e2: Aaron, I think they are asking if you could use a float type to store Boolean results – I don’t know C well enough to know whether it would work technically, but I’m going to go ahead and say it’s not a great idea even if it does.