# C Program to Print all Even Numbers from 1 to N using a while Loop

In this article, we will write a C program to print all even numbers from 1 to n using a `while` loop.

The program takes the value of N from the user as input and prints all the even numbers from 1 to n on the screen as output.

Sample Input:

``Enter the value of n: 10``

Output:

``All even numbers from 1 to 10 are: 2 4 6 8 10``

A number is called an even number if it is divisible by 2 such as 2, 4, 6, 8, etc. But if the number is not divisible by 2, it is called an odd number such as 1, 3, 5, 7, etc.

In C language, we can use the modulus operator(`%`) to check if the number is even or not. The modulus operator returns the remainder of dividing the first operand by the second operand.

For example, if we divide 5 by 2 using the modulus operator i.e. 5%2 the remainder would be 1, whereas dividing 6 by 2 using the modulus operator i.e. 6%2 gives 0. This means 5 is an odd number whereas 6 is an even number.

The following C program prints all the even numbers from 1 to n using a `while` loop:

```// C program to print all even numbers from 1 to n
#include <stdio.h>

int main(){

int i, n;

printf("Enter the value of n: ");
scanf("%d", &n);

printf("All even numbers from 1 to %d are: ", n);

i = 1;  // Initialize i with 1

// Run while loop until i reaches n
while(i<=n){

// Check if i is even
if(i % 2 ==0){
printf("%d ", i);
}

// Increment i by one on each iteration
i++;
}

return 0;

}```

Output:

```Enter the value of n: 10
All even numbers from 1 to 10 are: 2 4 6 8 10```

### Code Explanation:

• The program first asks the user to input the value of n and store it in the variable `n`.
• As we want to print all even numbers starting from 1, therefore, initialized `i=1` before running the `while` loop.
• The `while` loop checks if the current value of `i` is less than `n`, if yes, it continues. If not, it terminates.
• Inside the while loop’s body, the program checks if `i` is divisible by 2 using the modulus operator(`%`), if it is, the value of `i` is printed on the screen.
• In each iteration of the while loop, the value of `i` increments by 1 using the increment operator(`++`).

## Example 2: Print Even Numbers without using the If Statement

In the previous example, we used an `if` statement to check if the number is even or not. We can also print all the even numbers from 1 to n without using the `if` statement and make the program a bit optimal.

As we know, 2 is the smallest even number, therefore, to print all the even numbers between 1 and n, we can start from 2 and increment it by +2 every time the `while` loop runs.

The following C program prints all the even numbers from 1 to n without using the `if` statement:

```// C program to print all even numbers from 1 to n
#include <stdio.h>

int main(){

int i, n;

printf("Enter the value of n: ");
scanf("%d", &n);

printf("All even numbers from 1 to %d are: ", n);

i = 2;  // Since 2 is the smallest even number

// Run while loop until i reaches n
while(i<=n){

printf("%d ", i);

// Increment i by 2 to get next even number
i = i + 2;

}

return 0;

}```

Output:

```Enter the value of n: 10
All even numbers from 1 to 10 are: 2 4 6 8 10```

## Author

• Hi, My name is Manoj Kumar. I am a full-stack developer with a passion for creating robust and efficient web applications. I have hands-on experience with a diverse set of technologies, including but not limited to HTML, CSS, JavaScript, TypeScript, Angular, Node.js, Express, React, and MongoDB.