• C Program to Count Number of Digits in an Integer


    Counting the number of digits in an integer is a common task in programming. Whether you are working on a small project or a complex algorithm, the ability to count the digits in an integer can come in handy. In this blog post, we will walk through a C program that counts the number of digits in an integer using a while loop. We will also explore some concepts related to loops and integer manipulation in C.


    To fully understand and follow along with this tutorial, it would be helpful to have a basic understanding of the C programming language and familiarity with loops and variables.

    The C Program

    Let’s dive right into the C program that counts the number of digits in an integer. Below is the code that you can use as a starting point:

    #include <stdio.h>
    int main() {
        long long number;
        int count = 0;
        printf("Enter an integer: ");
        scanf("%lld", &number);
        // Counting the number of digits
        while (number != 0) {
            number /= 10;
        printf("Number of digits: %d\n", count);
        return 0;

    Understanding the Program

    The program starts by declaring two variables: number, which will hold the user-input integer, and count, which will keep track of the number of digits. We initialize count to 0, as we haven’t counted any digits yet.

    Next, we prompt the user to enter an integer using the printf function and read the input using the scanf function. The input is stored in the number variable.

    Now, we reach the most important part of the program – counting the digits using a while loop. The loop condition checks whether number is not equal to 0. As long as this condition is true, the loop will continue executing.

    Within the loop, we divide the number by 10 using the number /= 10 statement. This effectively removes the last digit from the number since integer division removes the remainder. We also increment the count variable by 1 using the ++count syntax. This process is repeated until the number becomes 0.

    Finally, we print the value of count using the printf function, which gives us the number of digits in the entered integer.

    Testing the Program

    Now that we have the program ready, let’s test it with a few sample inputs to see if it produces the correct output.

    Example 1:

    Enter an integer: 5372
    Number of digits: 4

    The input integer is 5372, which has 4 digits. The program correctly counts and displays the result.

    Example 2:

    Enter an integer: 0
    Number of digits: 1

    In this case, the input integer is 0, which is a special case. Although 0 doesn’t have any digits before it, we consider it as a single-digit number. Hence, the program correctly counts and displays 1.

    Example 3:

    Enter an integer: -12345
    Number of digits: 5

    The program also works correctly with negative integers. In this example, the input integer is -12345, which has 5 digits. The program ignores the minus sign and counts only the digits.

    Common Pitfalls

    While the program we discussed is simple and straightforward, there are a few common pitfalls that you should be aware of.

    1. Not initializing variables: It’s crucial to initialize variables before using them. In our program, we initialize count to 0 before starting the loop. If we forget to do this, the program may produce unexpected results.

    2. Incorrect loop condition: The loop condition number != 0 ensures that the loop will continue as long as number is not equal to 0. If we accidentally write number == 0 instead, the loop will never execute, and the program will incorrectly report 0 as the number of digits.

    3. Overflow issues: Our program uses the long long data type to handle large integers. However, there is still a limit to the size of integers that can be handled by this data type. If the input integer exceeds this limit, the program may produce incorrect results or even crash.


    In this blog post, we learned how to write a C program to count the number of digits in an integer using a while loop. We discussed the program’s code, explained its logic, and tested it with different sample inputs. We also highlighted some common pitfalls to avoid while working with such programs.

    Counting the number of digits in an integer is a fundamental skill in programming, and it forms the foundation for more complex tasks. By understanding the concepts and logic behind this program, you can apply the same principles to solve similar problems or build upon this program to create more advanced functionality.

    If you want to dive deeper into the world of C programming, we recommend exploring topics like integer manipulation, loop variations, or even implementing more complex algorithms. Happy coding!