Header files in helpers pset3

Question

What is the rationale for the header files in helpers.c? For example there is cs50.h but not stdio.h even though the functions are all stdio except for bool which is in neither CS50 nor helpers. And why include header.h, when the functions are written there in the file.

#include "cs50.c"
#include "helpers.c"       

/**
* Returns true if value is in array of n values, else false.
*/
bool search(int value, int values[], int n)
{

Thank you for your help!