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So I've got my good friend Winston here[br]to help us out with this one.

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And I know he already looks[br]impossibly awesome,

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but I think I want to change[br]his eye size a little bit.

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So here is where I draw his eyes.

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You can see we set the fill color,[br]and then drop two ellipses.

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And if I want to make[br]this ellipse smaller,

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I can change the width,[br]but then I also want it to be round,

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so I'm going to change the height[br]to be the same thing.

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And, well I want the eyes[br]to be the same size,

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so we should change the width[br]and the height of this eye.

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No, now the eyes are a little too small,[br]so I should change them back.

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Wouldn't I be great if I could[br]just change one number,

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and have both eyes change?

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And here is where <i>variables</i> come in.

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Now, a variable is just like a name[br]or a placeholder for something else.

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I like to think of a variable[br]as a big bucket with a name on it.

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You can put anything[br]you want in the bucket,

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but the name stays the same.

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We call the thing inside the bucket[br]the <i>value</i> of the variable.

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So let's start out by actually[br]making a variable.

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I'm going to do it all the way up here.

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All you do is type <i>var</i>,[br]which stands for variable,

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<i>Space</i>, and then[br]the name of the variable,

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which should describe[br]what the variable will hold.

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So I'm going to call this one <i>eyeSize</i>.

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And you can pretty much[br]name it whatever you want,

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but you're not allowed to have[br]spaces between words.

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And of course,[br]don't forget that semicolon!

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So now I've made[br]a variable called <i>eyeSize</i>,

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because it's going to hold[br]the size of Winston's eyes.

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But so far this variable[br]doesn't have a value yet.

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To give it one, we just say <i>eyeSize</i>,

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and then an <i>=</i>, and then <i>20;</i> .

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Okay, now see that equal sign?

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Forget whatever your math teacher[br]taught you about it.

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That equal sign does not mean "equals,"[br]it means assignment.

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This means we're assigning[br]the value <i>20</i> to the variable <i>eyeSize</i>.

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In other words,[br]we're putting the number 20

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into the bucket called, <i>eyeSize</i>.

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And remember how in math class[br]you can say stuff like,

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x = 3, and 3 = x,

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and it all means the same thing,[br]because <i>duuh</i>, they're equal?

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Well, you can't do that here, either.

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The thing on the left-hand side[br]of the equal sign

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is always the variable.

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And the thing on the right-hand side[br]of the equal sign is always the value

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that you are assigning to the variable.

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A good way to help you[br]remember which side is what

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is while you're coding[br]and talking out loud to yourself,

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like every cool programmer does,

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if you hit an equal sign[br]don't say "equals," say "gets."

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So this becomes, <i>eyeSize</i> gets <i>20</i>.

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And now, whenever I use[br]<i>eyeSize</i> in my program,

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the computer is going to be like,[br]"Oh yeah, that's a variable,

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I know what she <i>really</i> means[br]is this value 20."

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So check it out--[br]I'm just going to copy this,

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and then replace these four numbers

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with my new variable <i>eyeSize</i>,

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and Voila!

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Winston's eyes are now both[br]perfectly round and the same size,

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and if I want to change[br]the value of both eyes--

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or the size of both eyes,

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I can just change the value[br]of this one variable.

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Aah that's so cool!

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Okay, couple of last notes.

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Up here we made[br]a new variable called <i>eyeSize</i>.

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And here we gave it a value of <i>33</i>.

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We can actually do that all in one step

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by saying <i>var eyeSize</i>,[br]that's the first step,

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gets <i>33</i>,[br]that's the second step.

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And if I delete these two lines,

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you can see everything still works.

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Also remember that the computer[br]reads your code from top to bottom

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so the only reason it knew[br]what <i>eyeSize</i> was down here,

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was because we already[br]defined it up here.

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If I had put it down here instead,

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then once we got to this line of code,[br]the computer's going to be like,

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"<i>eyeSize</i>, what the heck is <i>eyeSize</i>?[br]I don't know what that is."

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In fact, here we get an error that says[br]<i>eyeSize</i> is not defined.

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And maybe you're thinking to yourself,

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"Yes, I did define it; it's right here!"

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But the computer's not smart,[br]and doesn't get that.

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So let's just move it back up to the top.

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And you've got to always make sure

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that you define your variable[br]before you try to use it.

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And now you know[br]about variables! Yaaay!