In the source code, you'll see it has a section with a few #includes
ex #include <stdio.h>
or #include "filename.h"
In this case, it is including a header file which sets up the prototypes for various functions, variables, and definitions, which will later be called upon in your program. (http://en.wikipedia.org/wiki/Header_file)
If you program calls one of these functions and the header file is not included, then you will get this error because the linker has no header files to get the definitions from

So, in order for your program to run, find the header file, and make sure that it is put in the same folder as your c program (if necessary)
This post was edited by oOn on Nov 23 2013 03:41pm