1. AP CSP: Sending Binary Messages
August 24-25, 2016

2. Sign up for Code.org
You need an address. If you have an address then go to code.org and create an account if you did not have one previously.
Once you have created your account then you can join the class using the following link.
Period 4:
Period 5:

3. Introduction
Computer science is commonly thought to be the study of computers themselves - the physical machines we have on our desks and carry around in our pockets. Another way that computer scientists think about would be to say that computer science is the study of information and information processes.
Today we’re going to think about what “information” and “information processes” means. What is it that you think you might be studying?
Now write in on a piece of paper from your binder the answer to the question: What is information(W.A.)? Once you’ve written down your response then talk about your answer with someone next to you.

4. Preparing for Binary Message Device Activity
Group up into pairs of two with the person directly in front of you. We are going to work with binary questions and messages. First come up with a binary question.
 Now that you’ve come up with a binary question, let’s talk about how you need to answer it. Answering a binary question is easy when we speak to each other, but it becomes more difficult when we are separated.
Today we will focus on how a binary message can be sent over a distance. You will build the device that sends them.

5. Sending Binary Messages Part 1:
You are going to build a device out of classroom supplies to send information to a classmate on the other side of the room. There are some basic rules and constraints: Stay on your side. You may not walk to the other side of the room. No language. That means no writing or talking to communicate. No projectiles!
You will have 5 minutes to construct a device out these supplies to send a simple binary message - one of the two possible answers to your binary question. You should try to make it fail-proof. Consider possible obstacles
Demonstrate how to use your device. Look around the room to see the different kinds of things people came up with.

6. Sending Binary Messages Part 2:
Not all questions have only two possible answers. Your new challenge is to invent a way to use your device to send an answer to a question that has 4 possible answers! Think about these things: Should you modify your device? Should you use it in a different way? Should you make a new device entirely? You have 8 minutes. Also record how you would use your device in words.
Demonstrate your device. Did you modify your device to add states? Did anyone not change the device but just use it differently.

7. Sending Binary Messages Part 3:
What if you wanted to ask an even more complex question with 8 possible answers?
Just as before update your device and test it out. Record how to use your device.
You’ve got 5 minutes!
How long can we keep doing this?

8. Sending Binary Messages Part 4:
Could we keep increasing the number of messages forever? Could our devices be used for questions with 16, 32, or 1,000,000 possible responses? Some things to think about…
How could you use your device to respond to much more complex questions (for example one with 1,000 possible responses). Come up with a system for using your device and describe it in such a way that another group could pick up your device and use it to send messages this way. Discuss this idea and write down how you would possibly accomplish this.

9. Wrap-up
Could you use another group’s device to send your set of messages? Why or why not? What would you need to know from the other groups?
Based on what you’ve seen in today’s activity what do you think are the limitations on the kinds of information we can send with binary messages?

10. Homework Questions Multiple Choice: A binary question is defined as:
A piece of information that is sent in pairs
Two questions which share the same answer
A message which can be in two possible states
A question which can be answered in only one of two possible ways
Provide an example of a question that could not be answered with a binary message. Explain why this is the case, making reference to the definition of a binary message.
Modify your question so that it could be answered with a binary message. Explain why it can now be answered with a binary message.
Can you send a message in binary to someone you’ve never before communicated with? If yes, how? If no, what does the person receiving a message need to know in order to successfully decode the message?
Why did you choose your particular message encoding strategy? List at least two reasons that justify your decision. List two issues or problems that could be improved in your encoding strategy.