C Program: Counting digits in an integer using Do-While Loop

Last update on March 18 2025 13:33:09 (UTC/GMT +8 hours)

10. Count Digits in a Number

Write a C program that implements a program to count the number of digits in a given integer using a do-while loop.

Sample Solution:

C Code:

#include <stdio.h>

int main() {
    int num;  // Declare a variable to store the input number
    int digitCount = 0;  // Initialize the count of digits

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

    // Take the absolute value of the entered number
    num = (num < 0) ? -num : num;

    // Handle the special case when the number is 0
    if (num == 0) {
        digitCount = 1;
    } else {
        // Count the number of digits using a do-while loop
        do {
            digitCount++;
            num /= 10;
        } while (num != 0);
    }

    // Print the count of digits
    printf("Number of digits: %d\n", digitCount);

    return 0;  // Indicate successful program execution
}

Sample Output:

Input an integer: 12345
Number of digits: 5

Input an integer: -789
Number of digits: 3

Input an integer: 000
Number of digits: 1

Explanation:

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

int num;: Declares a variable to store the input number.
int digitCount = 0;: Initializes a variable to store the count of digits.
printf("Enter an integer: ");: Prompts the user to input an integer.
scanf("%d", &num);: Reads the entered integer from the user.
(num < 0) ? -num : num;: Takes the absolute value of the entered number.
if (num == 0) { digitCount = 1; }: Handles the special case when the entered number is 0.
do { ... } while (num != 0);: Uses a do-while loop to count the number of digits.
digitCount++;: Increments the digit count for each digit encountered.
num /= 10;: Removes the last digit from the number.
printf("Number of digits: %d\n", digitCount);: Prints the count of digits.
return 0;: Indicates successful program execution.

Flowchart:

For more Practice: Solve these Related Problems:

Write a C program to count the number of digits in a number and determine whether the number is an Armstrong number.
Write a C program to count the number of digits in a number and calculate the sum of those digits.
Write a C program to count the number of digits and print each digit separately in reverse order.
Write a C program to count the number of digits in a number and check if all digits are unique.

C Programming Code Editor:

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