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One of the most important concepts of computer science,

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is how to define new commands;[br]how to add your own words to the computer language.

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Most computer languages have only about a hundred words or commands

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and the art is to define your own new words out of these coding blocks.

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We do this all the time at sports.

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In basketball you learn how to dribble, how to do a lay-up and how to rebound.

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Once you've learned these moves,[br]you learn new moves

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and put together these building blocks, [br]like a pick and roll or give and go

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and from there you can do more complex plays.

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Once you learned that play and give it a name,[br]everybody on the team knows how to do it.

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Simulary, once you learned a computer how to do an action once,

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using these sequence of commands,

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you can make up your own name for that action,[br]so it's easier to repeat it later.

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When you define your own command and give it a name,[br]it's called a function.

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If you are programming with blocks,

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you can use functions if there is a set of actions[br]which you are gonna use a lot of times.

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For example, you've written code to create a square,

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You could define this as a function called "create a square".

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Now you have a new block [br]that you can use multiple times to create multiple squares.

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A lot of simple functions can be used,[br]to create more complex patterns.

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In the next puzzle,

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the code you recently wrote to make a circle

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is available to you as a new function[br]that can make circles of different sizes.

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Can you use it to help Elsa to create a new beautiful pattern in the snow?