C Program to Calculate Factorial of a number using Recursion

Write a program to calculate the factorial of a number. Use the concept of recursion
instead of using loops.

#include<stdio.h>

main()

{

int a, fact;



printf("\nEnter any number: ");

scanf ("%d", &a);



fact=rec (a);

printf("\nFactorial Value = %d", fact);



}


rec (int x)

{

int f;



if (x==1)

return (1);

else

f=x*rec(x-1);



return (f);

}

Generation of Fibonacci Sequence using Recursion.

Write a recursive function to obtain the first 25 numbers of a Fibonacci
sequence. In a Fibonacci sequence the sum of two successive terms gives the
third term. Following are the first few terms of the Fibonacci sequence:

1 1 2 3 5 8 13 21 34 55 89 ...

#include<stdio.h>
main()
{

static int prev_number=0, number=1; // static: so value is not lost

int fibonacci (int prev_number, int number);

printf ("Following are the first 25 Numbers of the Fibonacci Series:\n");

printf ("1 "); //to avoid complexity

fibonacci (prev_number,number);


}



fibonacci (int prev_number, int number)

{
static int i=1; //i is not 0, cuz 1 is already counted in main.
int fibo;


if (i==25)
{
printf ("\ndone"); //stop after 25 numbers

}

else
{
fibo=prev_number+number;
prev_number=number; //important steps

number=fibo;

printf ("\n%d", fibo);
i++; // increment counter

fibonacci (prev_number,number); //recursion

}

}