One of the classic examples of using recursion is calculating a factorial of a number. Here’s a typical implementation of this function:

 int factorial (int num){ if (num==1)  return 1; return factorial(num-1)*num; // recursive call}

factorial() calls itself recursively, subtracting 1 from num on each call, until it equals 1. As always, you can use iteration instead of recursion:

 int factorial (int num){ int result=1; for (int i=1; i<=num; ++i)    result=result*=i; return result;}