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For the last loop we held your hand, so let’s try one on your own!

As an example of iteration, we have the first program ever to run on a stored-program computer (the EDSAC). It was written and run by David Wheeler in the computer laboratory at Cambridge University, England, on May 6th, 1948, to calculate and print a simple list of squares like the following:

``````0    0
1    1
2    4
3    9
4    16
5    25
6    36
7    49
8    64
9    81``````

On the left, there are numbers from 0 to 9. On the right are their squares. For example, for the number 9: 9 * 9 = 81.

Note: An algorithm like this is one of the easiest tells for needing a loop. But as you develop your programming skills, you’ll pick up more and more subtle hints and uses for where loops can be incorporated into your code!

### Instructions

1.

Write a `while` loop that prints out a number, followed by a tab `\t`, then the square of that number, followed by a new line `\n` like so:

``printf("%d\t%d\n", num, num * num);``

Have the `while` loop calculate this from 0 to 9.

Note: If you notice the Run button spinning continuously or a “Lost connection to Codecademy” message in this exercise, you may have an infinite loop! If the stop condition for our loop is never met, we will create a loop that never exits which prevents the program from ever completing. In this exercise, you can simply refresh the page to stop the infinite loop — then fix the code for your loop. However, we’ll talk more about infinite loops later, and even how to use them effectively!

2.

Now change your `while` loop to go backward from 9 and stop at 0. Your new output should look like this:

``````9    81
8    64
7    49
6    36
5    25
4    16
3    9
2    4
1    1
0    0``````