While loop

While loop is a programming loop which repeatedly execute a block of code as long as the specified condition returns True. The while loop starts with the while keyword, and it must include a boolean conditional expression inside brackets that returns either true or false. It executes the code block until the specified conditional expression returns false.

Before writing any loop be clear with your goal. If goal is not clear writing loop will be very difficult. Once the goal is clear ask yourself whats the starting point and termination point of the loop. Starting point and termination point is easy to figure out if goal is clear.

Syntax
while(condition) {
    //Code to be executed ;
}

NOTE
While studying loop we going to use some common terms called Increment, Decrement. Assume a variable called i, i++ is the short form of telling incrementing i value by 1, i-- is the short form of telling decrementing i value by 1. i+=10 is short form of increment i value by 10, i-=8 is the short form of decrementing i value by 8.

CODE

EG 1 . Printing 1 to 5 using While loop

static void Main(string[] args) {
    int i = 1;
    while (i<=5) {
        Console.WriteLine(i);
        i++;
    }
}

OUTPUT
1
2
3
4
5

CODE EXPLANATION
In the above code, our goal is to print from 1 to 5. The starting point of the loop will be 1 and termination point will be 5. So intially we created a variable called 'i' in order to store starting value. Now we need to print upto 5. So we written while loop with condition i<=5 so that loop will repeat exactly for 5 times since we are incrementing i value by 1 in each iteration.


EG 2 . Printing 5 to 1 using While loop

static void Main(string[] args) {
    int i = 5;
    while (i>=1) {
        Console.WriteLine(i);
        i--;
    }
}

OUTPUT
5
4
3
2
1

CODE EXPLANATION
In the above code, our goal is to print from 5 to 1. The starting point of the loop will be 5 and termination point will be 1. So intially we created a variable called 'i' in order to store starting value. Now we need to print upto 1. So we written while loop with condition i>=1 so that loop will repeat exactly for 5 times in reverse since we are decrementing i value by 1 in each iteration.


NOTE
We can create Infinite while loop, The syntax for creating Infinite while loop is as follows
    while(true){
        //Code to be executed ;
    }

Exercises
1. Print first 40 even numbers using while loop.
2. Find the sum of first 100 natural numbers using while loop.


(Click Here, For more exercises)