Write a program to accept a number and find sum of its individual digits repeatedly till the result is a single digit. [MAKAUT / WBUT MCA 2011]

Here we use two loop, one for sum the digits and another one use for checkthat sum result.

#include <stdio.h>
int main()
{
    int no,s=10;
    printf("Enter A No : ");
    scanf("%d",&no);
    while(s>9)
    {
        s=0;
        while(no>0)
        {
            s += no%10;
            no /= 10;
        }
        no=s;
    }
    printf("One Digit Sum is %d",s);
}

Output :

Enter A No :2345
One Digit Sum is 5