Complementary task for topic: 2

#include 

int main() {
    int number;
    
    printf("Enter a positive integer: ");
    scanf("%d", &number);
    
    if (number < 0) {
        printf("Invalid input. Please enter a positive integer.\n");
        return 0;
    }
    
    int sumOfDigits = 0;
    
    while (number != 0) {
        sumOfDigits += number % 10;
        number /= 10;
    }
    
    printf("The sum of digits in %d is %d.\n", number, sumOfDigits);
    
    return 0;
}

In this example, the program uses printf() to prompt the user to enter a positive integer. The scanf() function is used to scan the input from the user and store it in the number variable. The program checks if the number is negative. If it is negative, it prints an error message and terminates the program. Otherwise, it initializes the sumOfDigits variable to 0. The while loop continues as long as number is not equal to 0. In each iteration, it adds the rightmost digit of number to sumOfDigits using the modulus operator (%) and then divides number by 10 to remove the rightmost digit. Once number becomes 0, the loop terminates. Finally, it uses printf() to display the result.