Is there a function in C which checks whether a character is a character or integer, etc?

I have a a homework, and my professor said some of the students figured out that they could check whether the characters they read in are specific ones using a function. He said it was in the string.h library, but I checked and I don't see it. Can anybody point me in the right direction?

Can anybody point me in the right direction?

Look into the standard header ctype.h.

Side note, most of them are usually implemented as macros, see Plauger.