13.Factorial using recursion

 #include<stdio.h>

int factorial(int a);

int main(){

    int a;

    printf("Enter a number :");

    scanf("%d",&a);

    printf("\nThe factorial of %d is :%d",a,factorial(a));

   

    return 0;

}

int factorial(int a)

{

    if(a==0 ||  a==1)

    return 1;

    else

   return a*factorial(a-1);

}