# C Program to Find Sum of Digits of a Number

In C programming, it is often necessary to find the sum of the digits of a given number. In this program, we will write a C program that prompts the user to enter a number, calculates the sum of its digits, and prints the result.

Problem Statement

The problem statement is to write a C program that prompts the user to enter a number, calculates the sum of its digits, and prints the result.

Solution

Here is the C program to find the sum of digits of a number:

```#include <stdio.h>

int main() {
int num, sum = 0, remainder;

printf("Enter an integer: ");
scanf("%d", &num);

while(num > 0) {
remainder = num % 10;
sum += remainder;
num /= 10;
}

printf("The sum of digits is %d\n", sum);

return 0;
}
```

Output

Explanation

First, we include the `stdio.h` header file which is used for input and output functions. Then, we define the `main()` function as the starting point of our program.

We declare three integer variables – `num`, `sum`, and `remainder`. `num` is used to store the number entered by the user, `sum` is used to store the sum of the digits, and `remainder` is used to store the remainder obtained after dividing `num` by 10.

Next, we prompt the user to enter a number using the `printf()` function. The `scanf()` function is used to read in the number entered by the user. The format specifier `%d` is used to specify that the input should be read as an integer.

We then use a `while` loop to calculate the sum of the digits. In each iteration of the loop, we calculate the remainder of `num` divided by 10 using the modulo operator `%`. We add the remainder to the `sum` variable, and then divide `num` by 10 to remove the last digit from `num`. We repeat this process until `num` becomes 0.

Finally, we print the result using the `printf()` function. We use the format specifier `%d` to print the original number entered by the user, and `%d` again to print the sum of its digits.

Conclusion

In this tutorial, we learned how to write a C program to find the sum of digits of a number. We used a `while` loop to iterate through the digits of the number, and calculated the sum using the modulo operator `%` and division operator `/`. We also used the `printf()` function to print the result to the console.