Write a program to calculation of sum of the digit

Program:

#include<stdio.h>
#include<conio.h>
void main()
{
int n,r,sum=0;
printf("enter a number\n");
scanf("%d",&n);
while(n>0)
{
r=n%10;
sum=sum+r;
n=n/10;
}
printf("sum of digit of entered number %d",sum);
getch();
}

Output:

enter a number
420
sum of digit of entered number 6