C Program for Modulo Operator: Check Divisibility and Print Remainder

In C programming, the modulo operator (%) is a handy tool for determining the remainder when dividing two numbers. This is useful when you want to check if a number is divisible by another or when you need to find the remainder of a division operation. In this blog post, we will explain how the modulo operator works and provide a simple C program to demonstrate its usage.

What is the Modulo Operator?

The modulo operator (%) in C returns the remainder of the division of one number by another. For example:

• 10 % 3 returns 1 because when you divide 10 by 3, the remainder is 1.
• 9 % 3 returns 0 because 9 is evenly divisible by 3 with no remainder.

The modulo operator is often used in programming to check for divisibility and to calculate remainders.

Syntax of Modulo Operator:

result = a % b;

Here, a is the dividend, and b is the divisor. The result will store the remainder of a divided by b.

Example: C Program to Check Divisibility and Print Remainder

Let’s write a C program that uses the modulo operator to check whether a number is divisible by another and print the remainder.

#include <stdio.h>

int main() {
    int num1, num2, remainder;

    // Input two numbers
    printf("Enter two integers: ");
    scanf("%d %d", &num1, &num2);

    // Check if num2 is not zero to avoid division by zero
    if (num2 != 0) {
        // Calculate remainder using modulo operator
        remainder = num1 % num2;

        // Check if the number is divisible
        if (remainder == 0) {
            printf("%d is divisible by %d.\n", num1, num2);
        } else {
            printf("%d is not divisible by %d. Remainder: %d\n", num1, num2, remainder);
        }
    } else {
        printf("Division by zero is not allowed.\n");
    }

    return 0;
}

Explanation of the Program:

• Input: The program prompts the user to input two integers: num1 (the number to be divided) and num2 (the divisor).
• Modulo Operation: The modulo operator (%) is used to find the remainder when num1 is divided by num2.
• Divisibility Check: If the remainder is 0, the program outputs that num1 is divisible by num2. Otherwise, it prints the remainder.
• Error Handling: If the user enters 0 as the second number (num2), the program avoids division by zero and outputs an error message.

Sample Output

If the user enters 10 and 3 as input:

Enter two integers: 10 3
10 is not divisible by 3. Remainder: 1

If the user enters 9 and 3 as input:

Enter two integers: 9 3
9 is divisible by 3.

If the user enters 10 and 0 as input:

Enter two integers: 10 0
Division by zero is not allowed.

When to Use the Modulo Operator

The modulo operator is especially useful in the following scenarios:

1. Divisibility Checks: To check whether one number is divisible by another.
2. Cycling Through Values: For example, when iterating over a fixed-size array in a circular manner.
3. Finding Remainders: When you need to calculate the remainder after division, such as in time calculations.

The modulo operator is a powerful tool in C programming for performing mathematical operations involving division. By using it, you can easily check if a number is divisible by another and calculate the remainder. This is a simple yet fundamental operation that is widely used in programming.