CPP Tutorials

# Check Number is Even or Odd in CPP

## Introduction

In the world of programming, simple tasks often lead to powerful insights. One such task is determining whether a number is even or odd in C++. It might sound elementary, but this apparently clear concept holds essential value. In this article, we delve into the reasons behind the need to differentiate between even and odd numbers, explore the fundamental concept itself, and uncover the practical applications it offers. By understanding why we need this classification, what it entails, and how to implement it using C++, we unlock the door to more complex problem-solving and logic-building in programming.

## What Are Even and Odd Numbers in C++?

In the world of mathematics, numbers can be classified into two main categories: even numbers and odd numbers.

Even Numbers:
An even number is a whole number that can be evenly divided by 2, leaving no remainder. In other words, if you can divide the number by 2 and get a whole number result, then it’s an even number.

Odd Numbers:
On the other hand, an odd number is a whole number that cannot be divided evenly by 2. When you divide an odd number by 2, you’ll have a remainder of 1.

Examples:

• Even Numbers: 2, 4, 6, 8, 10, …
• Odd Numbers: 1, 3, 5, 7, 9, …

C++ Code Examples:
Here’s how you can determine whether a given number is even or odd using C++ code:

C++
``````#include <iostream>
using namespace std;

int main() {
int number;
cout << "Enter a number: ";
cin >> number;

if (number % 2 == 0) {
cout << number << " is an even number." << endl;
} else {
cout << number << " is an odd number." << endl;
}

return 0;
}``````

Output:

C++
``````Enter a number: 7
7 is an odd number.``````

Code Explanation:

• We start by including the necessary header file `#include <iostream>` which allows us to work with input and output.
• We declare an integer variable named `number` to store the user input.
• We prompt the user to enter a number using `cout` and get the input using `cin`.
• The `if` condition checks whether the remainder of dividing `number` by 2 is equal to 0.
• If the remainder is 0, the number is even, and the corresponding message is printed.
• If the remainder is not 0 (i.e., 1), the number is odd, and the corresponding message is printed.

In this way, the code determines whether a given number is even or odd and provides an appropriate output message.

To summarize:

• Even numbers are divisible by 2 without leaving a remainder.
• Odd numbers are not divisible by 2; they leave a remainder of 1 when divided by 2.
• C++ code can be used to determine whether a number is even or odd using the modulo operator (`%`).

## Understand by Detailed Diagram

• Start: The program begins.
• If number % 2 == 0: The program checks if the number is divisible by 2.
• Then Output ‘Even’: If the number is divisible by 2, it is even, and the program outputs “Even.”
• Else Output ‘Odd’: If the number is not divisible by 2, it is odd, and the program outputs “Odd.”
• End: The program ends.

## A Problem to Solve

Problem Statement:

Write a C++ program that takes an integer from the user and determines whether it’s an even or an odd number.

Requirements:

1. Input: An integer `n` that you will check. Prompt the user for this value.
2. Output: A message that says either “The number is even.” or “The number is odd.”, depending on the value of `n`.

Hints:

• You can use the modulo operator `%` to find the remainder of the number divided by 2.
• If a number is evenly divisible by 2 (i.e., the remainder when divided by 2 is 0), it is an even number.
• If the remainder when divided by 2 is not 0, the number is odd.

Example Code Structure:

C++
``````#include <iostream>
using namespace std;

int main() {
int number;

// Prompt the user for input
cout << "Enter an integer: ";
cin >> number;

// Check whether the number is even or odd
// TODO: Write the code to check the number

return 0;
}``````

Expected Output:

For input `10`, the output should be:

C++
``The number is even.``

For input `7`, the output should be:

C++
``The number is odd.``

## Examples of Using Even and Odd Numbers in C++

Let’s look at some examples to see how even and odd numbers can be used in C++. We’ll provide the code, the expected output, and a step-by-step explanation of how these are used.

### Example 1

C++
``````#include<iostream>
using namespace std;
int main() {
int num = 4;
if (num % 2 == 0) {
cout << num << " is even.";
} else {
cout << num << " is odd.";
}
return 0;
}``````

Output:

C++
``4 is even.``

Explanation:

• Purpose: The program checks if a number is even or odd.
• Input: The variable ‘num’ is initialized with the value 4.
• Conditional check: The program uses the modulo operator (%) to check if ‘num’ is divisible by 2 without a remainder.
• Output: Since 4 divided by 2 leaves no remainder, the program prints “4 is even.”
• Completion: The program exits after executing the code.

### Example 2

C++
``````#include<iostream>
using namespace std;
int main() {
int num = 7;
if (num % 2 == 0) {
cout << num << " is even.";
} else {
cout << num << " is odd.";
}
return 0;
}``````

Output:

C++
``7 is odd.``

Explanation:

• Purpose: The program checks if a number is even or odd.
• Input: The variable ‘num’ is initialized with the value 7.
• Conditional check: The program uses the modulo operator (%) to check if ‘num’ is divisible by 2 without a remainder.
• Output: Since 7 divided by 2 leaves a remainder of 1, the program prints “7 is odd.”
• Completion: The program exits after executing the code.

### Example 3

C++
``````#include<iostream>
using namespace std;
int main() {
int num = 0;
if (num % 2 == 0) {
cout << num << " is even.";
} else {
cout << num << " is odd.";
}
return 0;
}``````

Output:

C++
``0 is even.``

Explanation:

• Purpose: The program checks if a number is even or odd.
• Input: The variable ‘num’ is initialized with the value 0.
• Conditional check: The program uses the modulo operator (%) to check if ‘num’ is divisible by 2 without a remainder.
• Output: Since 0 is divisible by 2 without a remainder, the program prints “0 is even.”
• Completion: The program exits after executing the code.

## Key Takeaways

• Divisibility by 2: Even and odd numbers are a fundamental concept in mathematics and programming. Even numbers are perfectly divisible by 2, leaving no remainder, while odd numbers leave a remainder of 1 when divided by 2.
• Use in Divisibility Checks: Checking whether a number is even or odd can help us understand its divisibility by 2. This is particularly useful in programming scenarios where we need to determine if a number can be evenly divided or if there’s a remainder.
• Interactive Programs: Utilizing even and odd checks in your C++ programs can enhance interactivity. For example, you can create a program that takes a user’s input and informs them whether it’s an even or odd number, making your programs more engaging and user-friendly.
• Practical Applications: Understanding even and odd numbers can be beneficial for various practical applications. For instance, in games or simulations, you might want to alternate between even and odd elements to create interesting patterns or behaviors.
• Divisibility Rules: Even and odd numbers are part of divisibility rules that can simplify complex calculations. By identifying whether a number is even or odd, you can quickly determine its compatibility with certain mathematical operations or patterns.

## Conclusion

In conclusion, even and odd numbers are powerful tools in C++. By understanding how to use these, you can write better, more practical programs. So keep practicing, and soon you’ll be a pro at using even and odd numbers!

## FAQs

• What are even and odd numbers in C++?
Even numbers are integers that can be divided by 2 without a remainder, while odd numbers are integers that cannot be divided by 2 without a remainder.
• Why do we use even and odd numbers in C++?
We use even and odd numbers in C++ to check the divisibility of a number by 2. They allow our programs to provide useful feedback based on whether a number is even or odd.
• How do we use even and odd numbers in C++?
We use even and odd numbers in C++ by checking if a number divided by 2 has a remainder.
• Can using even and odd numbers make code more confusing?
Yes, if you use even and odd numbers incorrectly, it can lead to confusion and errors. It’s important to understand how these work and when to use them.
• What are some examples of using even and odd numbers in C++?
Some examples include checking if a number is even or odd, and providing different outputs based on whether a number is even or odd.