program9_06.c

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/* Program 9.6 Calculating factorials using recursion */
#include <stdio.h>

unsigned long factorial(unsigned long);

int main(void)
{
  unsigned long number = 0L;
  printf("\nEnter an integer value: ");
  scanf(" %lu", &number);
  printf("\nThe factorial of %lu is %lu\n", number, factorial(number));
  return 0;
}

/* Our recursive factorial function */
unsigned long factorial(unsigned long n)
{
  if(n < 2L)
    return n;
  else
    return n*factorial(n - 1L);
}