User Defined Functions in C

A functions is a self contained block of code, which are supposed to perform a particular task.
There are 2 types of function.
  1. Library Functions
  2. User Defined Functions
printf, scanf are examples for Library Functions.
main is an example for User Defined Funtions. main is a specially recognized funtion in C. Every program must have a main funtion to indicate the program where to begin to execution.
A program can have any other user defined functions along with main, but main is the funtion which starts to execution first.

All parts of user defined function are not essential, some of them can be absent. (For examle:Argument List)