Today we shall learn how to find the sum of digits of a given number using classes.Here we get the input a number for the user.Then we shall compute the sum of digits by grabbing each digit of the given number.For eg: if the given number is 143 then sum of digits in computed by 1+4+3=8.We get a doubt,how can we get the digits of given number.By dividing a number by 10 we get the last digit of it as remainder.For eg: 143/10 will give 3 has remainder.In this way we can get each and every digit of the given number.Now we shall write the code for it.

#include<iostream.h>
#include<conio.h>
class sumofdigits
{
  public:
     int n,r,result;
     void sum();
};
void sumofdigits :: sum()
{
  result=0;
  while(n>0)
  {
    r=n%10;
    n=n/10;
    result=result+r;
  }
  cout<<"Sum of digits of given number is:"<<result;
}
void main()
{
  clrscr();
  sumofdigits ob;
  cout<<"Enter a number:";
  cin>>ob.n;
  ob.sum();
  getch();
}

Output:
You can download the code:download