1. Sending Binary Messages
Lesson 1-2
AP Computer Science Principles

2. Objectives Students will be able to:
Create a device for sending a single bit of information - state A or state B - over a distance.
Analyze the possibilities and limitations that arise when sending binary messages.
Explain or demonstrate how to use a binary message sending device to send messages that have more than two states.

3. Journal
What is your personal definition of “information?”

4. Information
There are many ways we can think about the word “information,” but one possible definition we’ll explore today is that information is the answer to a question.
Perhaps the simplest question one can ask is what we’ll call a binary question, or a question to which there are only two possible answers.
For example, the question “Do we have a quiz today?” is a binary question, as there are only two possible responses, “yes” and “no.” Typically we think of binary questions as ones that can be answered “yes/no,” “true/false,” etc.

5. Binary Information
Many either/or type questions have binary responses as well, such as in “Which do you prefer: Coke or Pepsi?” or “Country music or hip hop?”
The information in this response we’ll call a binary message, or a message that can only have one of two possible values.

6. Definition of Binary
adjective : relating to or consisting of two things or parts Origin of BINARY Late Latin binarius, from Latin bini two by two First Known Use: 1597

7. Vocabulary
Binary Question: a question to which there are only two possible answers Binary Message: a message that can only be one of two possible values

8. Think about it…
You and your friend have not been able to communicate for the entire summer, and you have a chance to ask her one binary question that she will answer. What binary question do you want to ask?

9. Building a Binary Device
Your task is to create a device or method for sending a single binary message from one side of the room to the other without the sender or receiver moving location. That means that their device must be able to signal one of two possible states to someone standing on the other side of the room. Make it as foolproof as possible.

10. Rules (Yes There Are Always Rules!)
No language. You cannot communicate your selection with visual, written, or oral language. (e.g. you can’t just yell across the room or send notes with writing on them).
No projectiles. There can be no free-flying objects (e.g. you cannot throw things to each other).

11. In Your Journals… Question: _______________________________________
State
The possible messages (answers)
How to send with your device A B

12. Activity
You have 5 minutes!

13. Activity
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
The new question is:
What is your favorite season?
Four possible answers: Winter, Spring, Summer, Fall

14. Activity – Follow the instructions in the Activity Guide
Question: What is your favorite season?
Complete this part in your journal:
The possible messages
How to send with your device
Winter
Spring
Summer
Fall

15. Activity
You have 5 minutes!

16. Activity
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.

17. Activity – Follow the instructions in the Activity Guide
Complete this part in your journal:
The possible messages
How to send with your device
It is certain
You may rely on it
Outlook good
Reply hazy try again
Don't count on it
My reply is no
Outlook not so good
Very doubtful

18. Activity
You have 5 minutes!

19. Activity
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…
Our alphabet only has 26-letters, yet we can spell many words
Our number system only has 10 digits yet we can represent infinite numbers.

20. Activity
Think back to your simple two-state device. Could you simply use it differently, rather than modifying it?
Discuss with your partner: 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.

21. Code Studio
Go into Code Studio and complete the questions at the end of the Stage 2.

22. Hmmmmm…
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?