Header files Vs. Standard libraries

Header file is something like a reusible piece of code which can be included in other programs by including the corresponding header file.Thus if you want a generalised function to be added in other programs also then you will just create a header file containing the declaration for the function and save it with extension h.Then wherever you want to use it just include the header file and then just use the function from the header file.

header files is something that contains only the declarations what you are going to use in the program ... But the actual definition of the functions are defined in the Standard libraries .