A Function is a set of block statement code which is used for overcome the re-writes code in the project. The main benefits of Function is used for reusability the code and it works on various inputs, many of which are variables, and produces concrete results involving changes to variable values or actual operations based on the inputs. We can also say that a Function is a named procedure that performs a distinct service. The language statement that requests the function is called a Function call. Programming languages usually come with a compiler and a set of "canned" functions that a programmer can specify by writing language statements. These provided Functions are sometimes referred to as library routines. Some Functions are self-sufficient and can return results to the requesting program without help. Other functions need to make requests of the operating system in order to perform their work.