Program in C to find the sum of digits of a three digit number

Write a program in C to find the sum of digits of a three digit number

#include <stdio.h>

#include <math.h>

#include <conio.h>

main()

{

            int d,d1,d2,d3,r1,r2,sum;

            clrscr();

            printf("\n enter any three digit no's");

            scanf("%d",&d);

            d1=d/100;

            r1=d%100;

            if(r1!=0)

            {

                        d2=r1/10;

                        r2=r1%10;

                        if(r2!=0)

                                    d3=r2;

                        else

                                    d3=0;

            }          

            else

            {

                        d2=0;

                        d3=0;

            }

            sum=d1+d2+d3;

            printf("\n sum of 3 digit no is %d",sum);

            getch();

}