# C++ Program to Check Even or Odd Integers

05/04/2024

In computer programming, especially in languages like C++, determining whether a number is even or odd is a fundamental concept that illustrates the usage of arithmetic operators, conditional statements, and input/output operations. This basic yet insightful problem is not just about applying the modulus operator but also about understanding control flow and user interaction in C++. By crafting a program to check if an integer is even or odd, beginners can grasp essential programming constructs and their applications in solving real-world problems.

Understanding the Problem

The task is straightforward: given an integer, determine whether it is even or odd. An even number is an integer that is exactly divisible by 2, meaning it has no remainder when divided by 2. Conversely, an odd number is an integer that does leave a remainder when divided by 2. This definition immediately suggests the modulus (%) operator in C++, which returns the remainder of a division operation, as a tool to solve the problem.

Setting Up the Program

The first step in writing our C++ program is to include the necessary header files and use the standard namespace to simplify our code.

#include <iostream>

using namespace std;

These lines include the input/output stream library, which allows us to use cin for input and cout for output, and declare that we’re using the standard (std) namespace.

Taking User Input

Next, we prompt the user to enter an integer and store their input in a variable:

int main() {

int num;

cout << “Enter an integer: “;

cin >> num;

Here, int main() is the starting point of the program. We declare an integer variable num to hold the user’s input. We then use cout to display a prompt and cin to read the input.

Determining Even or Odd

Now, we use the modulus operator (%) to check if num is divisible by 2 without a remainder. If the result is 0, the number is even; otherwise, it’s odd. We use an if-else statement to implement this logic:

if (num % 2 == 0) {

cout << num << ” is even.” << endl;

} else {

cout << num << ” is odd.” << endl;

}

return 0;

}

This block is the core of our program. The condition in the if statement checks if num % 2 equals 0. If true, it executes the first block of code, printing that the number is even. If false, the else block executes, printing that the number is odd.

Complete Program

Combining all the parts, we have:

#include <iostream>

using namespace std;

int main() {

int num;

cout << “Enter an integer: “;

cin >> num;

if (num % 2 == 0) {

cout << num << ” is even.” << endl;

} else {

cout << num << ” is odd.” << endl;

}

return 0;

}

Key Concepts illustrated

• Modulus Operator:

This program illustrates the use of the modulus operator (%) to find the remainder of division, which is pivotal in many programming scenarios beyond checking for even or odd numbers.

• Conditional Statements:

The if-else statement is a fundamental control flow mechanism that allows the program to execute different blocks of code based on certain conditions.

• User Input and Output:

Through cin and cout, the program demonstrates how to interact with users by taking input and providing output, making it dynamic and interactive.

Enhancements and Best Practices:

• Input Validation:

Adding checks to ensure the user enters a valid integer enhances the robustness of your program.

• Function Usage:

Encapsulating the logic for checking even or odd numbers in a function improves code organization and reusability. For example, you could create a function bool isEven(int num) that returns true if num is even and false otherwise.

• Handling Large Numbers:

For very large integers, ensure your program’s data types can accommodate the size. In cases where int might not suffice, long long could be used.