This Program is used to Find the sum of the digits of a number repeatedly until we get a single digit output. For example if we take a number : 1234, it will be calculated as 1+2+3+4 = 10 then 1+0 = 1. So the final Result will be 1.

First we are requesting the user an input. Then we are storing it in the variable `n`

. Then we are diving the given number by 9 and using the modulus operator to get the remainder. Then if given number is 0, we are printing that the Single Digit is 0 else we are checking the number in the `rem`

variable. If it is 0 then the resulting single digit will be 9 else we will print the value present in `rem`

variable.

## C Program to perform Sum of Digits until Single Digit is obtained

#include<stdio.h> #include<conio.h> void main() { int n,rem; printf("\nEnter a number : "); scanf("%d",&n); rem = n%9; if(n==0) { printf("\nSingle digit result is 0"); } else { if(rem==0) printf("\nSingle digit result is 9"); else printf("\nSingle digit result is %d",rem); } getch(); }

The above program can also be written as the following:

#include<stdio.h> #include<conio.h> void main() { int n,rem,sum = 0; printf("\nEnter a number : "); scanf("%d",&n); while(n > 0) { while(n != 0) { rem = n%10; sum = sum+rem; n=n/10; } if(sum > 9) { n = sum; sum = 0; } } printf("%d",sum); getch(); }

Output: