Library Funciton

C contains a number of built-in functions for doing commonly used tasks. So far we have used atoi, printf, sizeof, strtok, and sqrt. To get full details of any built-in library function all we have to do is type for example:

and we will see all this:

Which pretty-well tells you everything you need to know about this function and how to use it and variants of it. Most importantly it tells you which header ile to include.