Fix digit summation logic and add comments

digits_sum.c

@@ -1,15 +1,26 @@
-#include <stdio.h>
+#include <stdio.h> 
 
+/*
+ Calculates and prints the sum of the digits of an integer entered by the user.
+ This program prompts the user to enter a number and then uses a while loop
+ to iteratively extract and sum the individual digits of that number.
+ prints the Sum of digits
+ */
+
 int main() {
     int num, sum = 0, digit;
-
     printf("Enter a number: ");
     scanf("%d", &num);
 
     while(num != 0) {
-        digit = num % 100;
+        // 1. Extract the last digit: The modulo operator (%) gives the remainder when divided by 10.
+        digit = num % 10;
+
+        // 2. Add the extracted digit to the running sum
         sum += digit;
-        num /= 100;
+
+        // 3. Remove the last digit: Integer division (/) by 10 truncates the last digit.
+        num /= 10;
     }
 
     printf("Sum of digits = %d\n", sum);