sum of digits in a number

#include<stdio.h>
#include<math.h>
#include<conio.h>
void main()
{
    int a,b,sum=0;                                                                  
    printf("enter the number");
    scanf("%d",&a);
    while(a>0)
    {
        b=a%10;
        a=a/10;
        sum=sum+b;
    }
    printf("the sum of digits of a number %d",sum);
    getche();
}