In programming, developers often require a repeated execution of a sequence of operations. A loop is a basic programming construct that allows repeated execution of a fragment of source code.
In a while loop, the code is repeated a fixed number of times or it repeats until a given condition is true.
while (condition)
{
body loop;
}
Let's consider a very simple example of using the while loop.
// Initialize the counter
int counter = 0;
// Execute the loop body while the loop condition holds
while (counter <= 5)
{
// Print the counter value
Console.WriteLine("Number: " + counter);
// Increment the counter
counter++;
}
It will print the numbers in the range from 0 to 4 in ascending order on the console window.
Number: 0
Number: 1
Number: 2
Number: 3
Number: 4
The do-while loop is similar to the while loop, but it checks the condition after each execution of its body loop.
do
{
executable code;
}
while (condition);
The body of the do-while loop will execute at least once irrespective of the test-expression.
Let's consider the same example of using the do-while loop.
// Initialize the counter
int counter = 0;
// Execute the do-while body loop
do
{
// Print the counter value
Console.WriteLine("Number: " + counter);
// Increment the counter
counter++;
}
while (counter <= 5);
It will print the numbers in the range from 0 to 5 in ascending order on the console window.
Number: 0
Number: 1
Number: 2
Number: 3
Number: 4
Number: 5
You can see that do-while is executed one more time and that is because the condition is checked after the body is executed, but in while loop, the condition is checked at the start.