# 1. Introduction

In programming, sometimes it's not just the quotient of a division that's valuable, but also the remainder. Finding the remainder is a crucial operation in many algorithms and has applications ranging from simple arithmetic to cryptographic algorithms. Today, we will create a C program to obtain the remainder when one number is divided by another.

# 2. Program Overview

Our program will:

1. Ask the user for two numbers: a dividend and a divisor.

2. Capture and store these values.

3. Compute the remainder of the division.

4. Present the remainder to the user.

# 3. Code Program

``````#include <stdio.h>  // Integrate the Standard I/O library for input and output functionalities

int main() {  // The main function, marking the beginning of our program

int dividend, divisor, remainder;  // Declare three integer variables to keep the user's input and the computation result

// Interact with the user for their input
printf("Enter the dividend (the number to be divided): ");
scanf("%d", &dividend);  // Obtain and store the dividend

printf("Enter the divisor (the number to divide by): ");
scanf("%d", &divisor);  // Obtain and store the divisor

// Check if the divisor is zero, as division by zero is undefined
if (divisor == 0) {
printf("Error! Division by zero is not permissible.\n");
return 1;  // Terminate the program with an error code
}

remainder = dividend % divisor;  // Calculate the remainder

printf("The remainder when %d is divided by %d is: %d\n", dividend, divisor, remainder);  // Display the computed remainder

return 0;  // Indicate that the program executed successfully
}
``````

### Output:

```Enter the dividend (the number to be divided): 17
Enter the divisor (the number to divide by): 4
The remainder when 17 is divided by 4 is: 1
```

# 4. Step By Step Explanation

1. #include <stdio.h>: This inclusion provides us access to core input/output functions, allowing communication with the user.

2. int main(): The central function where every C program begins its lifecycle.

3. int dividend, divisor, remainder;: This line reserves space in memory for three integer variables that will contain the dividend, divisor, and the resultant remainder.

4. The functions printf and scanf: They facilitate the communication process with the user, displaying prompts and recording input respectively.

5. The check if (divisor == 0): Before diving into the calculation, it's essential to confirm that the divisor isn't zero. Division by zero isn't defined in mathematics and would lead to unpredictable program behavior.

6. remainder = dividend % divisor;: This line uses the modulus operator (%) to compute the remainder of the division.

7. return 0;: A convention indicating the successful termination of the program. An attempt to divide by zero will prematurely end the program with return 1;, signaling an error.

This exercise not only introduces the modulus operator but also demonstrates the importance of error-checking in programs to ensure they're robust and user-friendly.