C Program To Count Number of Digits in an Integer

In this post, we will learn how to count number of digits in an integer using the C Programming language.

This program will take an integer from the user and read the integer and count the total number of digits in the integer. For example: If the user enters the integer 5464, then the output will be 4.

So, without further ado, let’s begin the tutorial.

C Program To Count Number of Digits in an Integer

// C Program To Count Number of Digits in an Integer
#include <stdio.h>
int main(){
    int num;
    
    // Asking for Input
    printf("Enter an Integer: ");
    scanf("%d", &num);
    
    //logic
    int count = 0;
    
    while (num > 0){
        count++;
        num /= 10;  //can also write num = num / 10
    }
    printf("Total Number of Digits are: %d", count);
    return 0;
}

Output

Enter an Integer: 1829
Total Number of Digits in 1829 are: 4

How Does This Program Work ?

    int num;

In this program, we have declared a variable names as num.

    // Asking for Input
    printf("Enter an Integer: ");
    scanf("%d", &num);

Then, the user is asked to enter the integer. The value of the integer will be stored in the num variable.

    //logic
    count = 0;
    
    while (num > 0){
        count++;
        num /= 10;
    }

• After the first iteration, the value of the num will be 182 and the count is incremented to 1.
• After the second iteration, the value of the num will be 18 and the count is incremented to 2.
• After the third iteration, the value of the num will be 1 and the count is incremented to 3.
• After the fourth iteration, the value of the num will be 0 and the count is incremented to 4.
• Then, the test expression of the loop is evaluated false and the loop terminates.

Some of the used terms are as follow:

#include <stdio.h> – In the first line we have used #include, it is a preprocessor command that tells the compiler to include the contents of the stdio.h(standard input and output) file in the program. 

The stdio.h is a file which contains input and output functions like scanf() and printf() to take input and display output respectively. 

Int main() – Here main() is the function name and int is the return type of this function. The Execution of any Programming written in C language begins with main() function. 

scanf() – scanf() function is used to take input from the user.  

printf() – printf() function is used to display and print the string under the quotation to the screen.  

while Loop – In the while loop, the statements inside the body of the while loop keeps executing until it is evaluated to False.

// – Used for Commenting in C. 

C Program To Count Number of Digits Using User Defined function

// C Program To Count Number of Digits in an Integer 
#include <stdio.h>

int countDigits(int num)
{
    int count = 0;
    while (num > 0){
        count++;
        num = num / 10;
    }
    return count;
}

int main()
{
    int num, a;
    
    // Asking for Input
    printf("Enter an Integer: ");
    scanf("%d", &num);
    
    // logic
    a = countDigits(num);
    printf("Total Number of Digits in %d are %d.", num, a);
    return 0;
}

Output

Enter an Integer: 12345
Total Number of Digits in 12345 are 5

C Program To Count Number of Digits Without Using Loops

// C Program To Count Number of Digits in an Integer Without Using Loops
#include <stdio.h>
#include <math.h>

int main(){
    int num;
    int count = 0;
    
    // Asking for Input
    printf("Enter an Integer: ");
    scanf("%d", &num);
    
    // logic
    if (num > 0)
    {
        count = (num == 0) ? 1  : (log10(num) + 1);
        
        printf("Total Number of Digits in %d are %d", num, count);
    }
    else{
        printf("Enter Positive Integer\n");
    }
    return 0;
}

Output

Enter an Integer: 8484985
Total Number of Digits in 8484985 are 7

Conclusion

I hope after going through this post, you understand how to count the number of digits in an integer using C Programming language.

If you have any doubt regarding the topic, feel free to contact us in the Comment Section. We will be delighted to help you.