What is Factorial ?

Factorial of a no. means multiplying below numbers. Factorial is denoted by ! Exclamation mark
Eg:- 5! means :- 5 * 4 * 3 * 2 * 1 = 120

What is a Recursive function?

Definition:- A function which calls itself is called as Recursive function & technique is called as Recursion

Program for factorial of a number using recursive function in C

#include<stdio.h>
#include<conio.h>
int fn(int n);
void main()
{
    int num, f;
   clrscr();
   // Enter the number for factorial 
   printf(\n Enter the number:-);
   scanf(%d, num);
   f=fn(num);
   printf(\n The Factorial number:-%d,f);
   getch();
}
   int fn(int n)
   { 
       int y;
       if ((n==0)||(n==1))
           y=1;
      else
            y=n*fn(n-1);
            return(y);
  }

Output:-

Enter the number:- 5
The Factorial number:- 120