One of the great things in computer programming
is once you've taught a computer how to do
an action, you can call that function again.
You give it a name and then you can call it.
That's really like extending the language.
In the program we built, we learned how to
draw a square by moving and turning four times.
We can take that function and give it a name,
draw a square, so that any time we want to
do that, we simply say draw a square and it
will go back and invoke that function, that
code. It will get done for us. We've added
that concept to our programming language.