How Do-While Loops Work in Computer Programming

Contrast With While and For Loops

How does a do-while loop differ from other loops? The most important distinction is that do-while loops test a condition after executing a code block, while other loops check a condition before running the code inside.computer science computer science computer science computer science computer science

Consider this basic pseudocode while loop for comparison:

x = 10;

while (x < 5) {
  output "The loop has run!";
  x++;
}

Here, x is set to 10 and the while loop checks that x is less than 5 before it runs. Because of this, the code inside never runs. Applying the same logic to a do-while loop gives us something like this:

x = 10;

do {
  output "The loop has run!";
  x++;
} while (x < 5)

This loop will output the text once, increment x, then continue on.

Note that you can re-create the do-while functionality with an extra statement in front of a while loop, like so:

output "Hello!";
x++;
while (x < 5) {
  output "Hello!";
  x++;
}

However, this is clunky and there’s no reason to do it when do-while loops exist.

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