C PROGRAMMING PROGRAM • CONTROL FLOW & LOOP FORMS

Find a Digit Sum Using a do-while Loop

Learn how to find a digit sum using a do-while loop using a clear C program.

Beginnerdo-whileDigitsGuaranteed iteration

PROBLEM UNDERSTANDING

Input and expected output

Sample input

Sample output

Digit sum = 11

COMPLETE C PROGRAM

Complete C implementation

#include <stdio.h>

int main(void)
{
    int number, sum = 0;
    printf("Enter a non-negative integer: ");
    scanf("%d", &number);
    do {
        sum += number % 10;
        number /= 10;
    } while (number != 0);
    printf("Digit sum = %d\n", sum);
    return 0;
}

CURRENT STEP

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SELECTED LINE

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EXPECTED OUTPUT FOR THE SAMPLE

Digit sum = 11

0%Step 0 of 0

PROGRAM EXPLANATION

Algorithm and explanation

Read the required input values.
Execute the digit-processing body once before testing whether digits remain.
Display the computed result.

Execute the digit-processing body once before testing whether digits remain.

EFFICIENCY

Time and space complexity

Time complexity

O(d)

Auxiliary space

O(1)

DEBUGGING CHECKLIST

Common mistakes

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Use the correct format specifier for every variable.

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Initialize variables before using their values.

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Check braces, semicolons and input order carefully.

Try it yourself

Practice: Run the program with the sample input, predict its output, and then test one boundary case of your own.