What is the use of header file in C language?

In C language when you write a program,it is need to call the header file for your different type of opperation which you done in the programme . If you don’t call a header file ,in the time of executation of the program it can not done the work .

Header files provide the definations and declerations for the library functions.
So each header file contains the library functionss along with the necessary definations and declerations.