C Program: Calculate Sum of squares of digits with Do-While Loop

Last update on July 30 2025 12:56:17 (UTC/GMT +8 hours)

6. Sum of Squares of Digits

Write a C program that prompts the user to enter a positive integer and then calculates and prints the sum of the squares of each digit in that number using a do-while loop.

Sample Solution:

C Code:

#include <stdio.h>

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

    // Prompt the user to enter a positive integer
    printf("Input a positive integer: ");
    scanf("%d", &num);

    // Check if the entered number is positive
    if (num <= 0) {
        printf("Please input a positive integer.\n");
        return 1; // Return an error code
    }

    // Calculate the sum of the squares of each digit
    do {
        digit = num % 10;  // Extract the last digit
        sum += digit * digit;  // Add the square of the digit to the sum
        num /= 10;  // Remove the last digit

    } while (num != 0);  // Continue the loop until there are no more digits

    // Print the sum of the squares of each digit
    printf("Sum of the squares of each digit: %d\n", sum);

    return 0; // Indicate successful program execution
}

Sample Output:

Input a positive integer: 1234
Sum of the squares of each digit: 30

Explanation:

Here are key parts of the above code step by step:

int num, digit, sum = 0;: Declares variables to store the entered number ('num'), each digit ('digit'), and the sum of the squares of digits ('sum').
printf("Input a positive integer: ");: Prompts the user to input a positive integer.
scanf("%d", &num);: Reads the entered integer from the user and stores it in the variable num.
if (num <= 0) { ... }: Checks if the entered number is positive. If not, it displays an error message and returns an error code.
do { ... } while (num != 0);: Starts a do-while loop to iterate through each digit of the entered number.
digit = num % 10;: Extracts the last digit of the number.
sum += digit * digit;: Adds the square of the extracted digit to the sum.
num /= 10;: Removes the last digit from the number.
The loop continues until there are no more digits in the number.
printf("Sum of the squares of each digit: %d\n", sum);: Prints the calculated sum of the squares of each digit.
return 0;: Indicates successful program execution.

Flowchart:

For more Practice: Solve these Related Problems:

Write a C program to compute the sum of cubes of digits of a given number using a do-while loop.
Write a C program to find the sum of squares of digits of a given number, but exclude squares of odd digits.
Write a C program to find the sum of squares of digits and check if the sum is a prime number.
Write a C program to compute the sum of squares of digits until the sum itself is a single-digit number.

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