Basic question -3 (simple recursion)

This time  we are going to discuss simple recursion .
  what is recursion : It is simply a solving technique to solve function which uses its previous volue.
                         example : Xn = Xn-1 + 2.

recursion

 It is very  basic example.we can use this technique  in computer science to solve such type of problem very effectivelly . example traversal of tree, find factorial etc.

So your Today's challenge is : Make a program to take integer with any no of digits as input & find sum of digits of that integer using  :  2 method

1 => looping

2 => Recursion

example : if integer is 94356 then sum of digits = 9+4+3+5+6 =27.

C Program :

                                        Using while loop :

 #include<stdio.h>  
 main()  
 {  
       int n,sum=0,p;  
       printf("input any ineger volue : ");  
       scanf("%d",&n);  
       while(n > 0) //   
       {  
            p=n%10; // give remainder  
            sum=sum+p; // count sum   
            n=n/10; // approx integer of divison i.e 13/10 = 1;  
       }      // as integer/integer = integer if u wan't in float u need to do typecasting  
       printf("sum of digit is : %d",sum);  
 }  

Using recursion function :

 #include<stdio.h>  
 int sum_of_digits(int,int *); // function declaration  
 main()  
 {  
       int n,sum=0;  
       printf("input any ineger volue : ");  
       scanf("%d",&n);  
       sum_of_digits(n,&sum);  
       printf("sum of digit is : %d",sum);  
 }  
 int sum_of_digits(int a,int *sum)  
 {   
    int p;  
   if(a)  //basicaly it is condition a>0  
   {    //for a=0 if condition will be false.  
    p=a%10;  
    *sum=*sum+p;  
    sum_of_digits(a/10,sum);  
   }  
      return 0;  
 }  

OUTPUT : 

Sum of digits using recursion & loop