Lesson goal: The while-loop: introduction

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By this time, you hopefully understand a few things. The first is the for-loop and the second is the ability to ask the computer true/false questions. Lastly, with the if-statement you were able to make the computer react to the result of a true/false question.

Like the for-loop, the while-loop can cause the computer to execute a chunk of code over and over again. But unlike the for-loop, which is primarily used for counting, the while-loop can loop over and over again without doing any counting at all! In fact, a while-loop will run a chunk of code over and over again, until a true/false condition you give it becomes false. It is a very useful looping structure.

Let's start with a simple example that mimics the for-loop, and does a bit of counting.

while condition do

Move the mouse over a dotted box for more information.

Now you try. Put a condition in the while ... do line to have the computer count from 1 to 10.

Type your code here:

See your results here:

This code will not run! What condition will you put in the while loop to cause it to count in the variable a from $1$ to $10$? In other words, you want to keep the while loop going as long as a is less than or equal to 10. Dismiss.
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