Recursion in c Language

                                                        Recursion
Recursion  is  the  process  of  repeating  items  in  a  self-similar  way.  Same  applies  in
programming languages as well where if a programming allows you to call a function inside
the same function that is called recursive call of the function as follows.
void recursion()
{
recursion(); /* function calls itself */
}
int main()
{
recursion();
}
The  C  programming  language  supports  recursion,  i.e.,  a  function  to  call  itself.  But  while
using  recursion,  programmers  need  to  be  careful  to  define  an  exit  condition  from  the
function, otherwise it will go in infinite loop.
Recursive  function  are  very  useful  to  solve  many  mathematical  problems  like  to  calculate
factorial of a number, generating Fibonacci series, etc.
Number Factorial
Following  is  an  example,  which  calculates  factorial  for  a  given  number  using  a  recursive
function:
#include <stdio.h>
int factorial(unsigned int i)
{
if(i <= 1)
{
return 1;
}
return i * factorial(i - 1);
}
int  main()

{
int i = 15;
printf("Factorial of %d is %d\n", i, factorial(i));
return 0;
}
When the above code is compiled and executed, it produces the following result:
Factorial of 15 is 2004310016

Fibonacci Series
Following is another example, which generates Fibonacci  series for a given number using a
recursive function:
#include <stdio.h>
int fibonaci(int i)
{
if(i == 0)
{
return 0;
}
if(i == 1)
{
return 1;
}
return fibonaci(i-1) + fibonaci(i-2);
}
int  main()
{
int i;
for (i = 0; i < 10; i++)
{
printf("%d\t%n", fibonaci(i));
}
return 0;
}
When the above code is compiled and executed, it produces the following result:
0 1  1  2  3  5  8  13  21  34