# While Loop in Dart

In this tutorial, we will learn about *while* loop in Dart. We will cover the basics of iterative execution using while loops.

## What is a While Loop

A *while* loop is a control flow statement that allows code to be executed repeatedly based on a given Boolean condition. The loop runs as long as the condition evaluates to true.

## Syntax

The syntax for the *while* loop in Dart is:

```
while (condition) {
// Code block to be executed
}
```

The *while* loop evaluates the condition before executing the loop's body. If the condition is true, the code block inside the loop is executed. This process repeats until the condition becomes false.

## Example 1: Printing Numbers from 1 to 5

- Declare an integer variable
`i`

. - Initialize
`i`

to 1. - Use a while loop to print numbers from 1 to 5.

#### Dart Program

```
void main() {
int i = 1;
while (i <= 5) {
print(i);
i++;
}
}
```

#### Output

1 2 3 4 5

## Example 2: Calculating the Sum of First N Natural Numbers

- Declare two integer variables:
`n`

and`sum`

. - Assign a value to
`n`

. - Initialize
`sum`

to 0. - Use a while loop to calculate the sum of the first
`n`

natural numbers. - Print the sum.

#### Dart Program

```
void main() {
int n = 10;
int sum = 0;
int i = 1;
while (i <= n) {
sum += i;
i++;
}
print('Sum of first $n natural numbers is $sum');
}
```

#### Output

Sum of first 10 natural numbers is 55

## Example 3: Reversing a Number

- Declare three integer variables:
`num`

,`rev`

, and`digit`

. - Assign a value to
`num`

. - Initialize
`rev`

to 0. - Use a while loop to reverse the digits of
`num`

. - Print the reversed number.

#### Dart Program

```
void main() {
int num = 12345;
int rev = 0;
while (num != 0) {
int digit = num % 10;
rev = rev * 10 + digit;
num ~/= 10;
}
print('Reversed number is $rev');
}
```

#### Output

Reversed number is 54321