Sum of Digits of Number C Program

By | September 16, 2015

C Program To Calculate Sum of Digits of Number

Learn How To Calculate Sum of Digits of Number in C Programming Language. It is important that we should know How A For Loop Works before getting further with the C Program Code. This Sum of Digits of a Number C Program makes use of While and For Loops and demonstrates working with User Defined function as well.

Algorithm To Find Sum of Digits of a Number

  • Fetch the Number from the User
  • Get the Last Digit of a Number using Modulus Operator
  • Add the Last Digit in the Sum variable
  • Now, Remove the Last Digit by using Division Operator

You need to perform the above operations in a loop till the condition (num > 0) is True. This method will fetch you the Sum of Digits of a Number entered by the User.

Example

Sum of Digits of 1234 = 10

Method 1: C Program To Calculate Sum of Numbers of an Integer with While Loop

#include<stdio.h>

int main()
{
    int num, rem, sum = 0;
    printf("\nEnter a Number:\t");
    scanf("%d", &num);
    while(num > 0)
    {
        rem = num%10;
        sum = sum + rem;
        num = num/10;
    }
    printf("\nSum of Digits of the Number: \t%d\n", sum);
    return 0;
}

Method 2: Find Sum of Digits of Number in C Programming using For Loop

#include<stdio.h>

int main()
{
    int num, rem, sum = 0;
    printf("\nEnter a Number:\t");
    scanf("%d", &num);
    for(; num > 0;)
    {
        rem = num%10;
        sum = sum + rem;
        num = num/10;
    }
    printf("\nSum of Digits of the Number: \t%d\n", sum);
    return 0;
}

Output

C Program To Find Sum of Digits of Number

In case you get any compilation errors in this C Program To Calculate Sum of Digits of Number or you have any doubts about it, let us know about it in the Comment Section below.

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4 thoughts on “Sum of Digits of Number C Program

  1. Sneha Mishra

    Why do we have to use Modulus Operator in this C Program to calculate addition of digits in the integer?

    Reply
  2. Jas Arora

    Thanks! I finally understood the difference between how a for loop works and a while loop works with this Sum of Digits code in C programming.

    Reply
    1. Tushar Soni Post author

      Yes. It is important to initialize the sum to zero because by default, the automatic variables in C contains garbage values. It will not give an accurate answer if the sum is not zero at the start.

      Reply

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