Question

what is the use of header file

Answer 1

A header file is generally used to define all of the functions, variables and constants contained in any function library that you might want to use. The header file stdio.h should be used if you want to use the two standard I/Ofunctions printf and scanf.

Answer 2

Header files are used as the basic documentation where the description of the data types or the definitions of general functions (i.e. the printf()  function in C) are declared.These header files are included in your programs so that the above mentoined things (functions and data types,don't know if they are "things" XD) can be used in the particular program.

hope you get your answer :)