In this lesson we work in groups using classroom supplies and everyday objects to develop our own systems for encoding and sending simple binary messages, messages that only have two possible values. We will think about what can be usefully conveyed in such a simple message and build a "device" to communicate the message over some physical distance. Then we are asked to consider how to use your binary messaging devices to send a more complex message - a message with more than two possibilities, say four, or eight, or even thousands of different messages. We will collaborate in an iterative design process in the "maker ethos" of rapidly building and improving their "device" for sending messages.
- Binary: a way of representing information using only two options.
- Bit: a contraction of "Binary Digit"; the single unit of information in a computer, typically represented as a 0 or 1
Students will be able to:
- One of the least understood things about the internet is how it works as a physical system. Bits of information physically travel across the system from one place to another. On the "real" internet bits are transmitted using a variety of different mediums, and most of the time a single bit physically travels over a variety of systems to get where it’s going. Students should see the issues in the physical transmission of bits as a separate problem from interpreting and encoding the messages sent on top of those systems.
- While building and modifying their "binary message devices" students should recognize that it's easier to invent a system of communication that uses combinations of binary signals with a simple device, rather than making a new, or increasingly complex device for each new problem. This lays the foundations for encoding complex information in computers using combinations of bits, and developing clear communication protocols.
One of the least understood things about the internet is how it works as a physical system. Bits of information physically travel from one place to another. On the "real" internet bits are transmitted using a variety of different mediums, and most of the time a single bit physically travels over a variety of systems to get where it’s going. Students should see the issues in the physical transmission of bits as a separate problem from interpreting and encoding the messages sent on top of those systems.
While building and modifying their "binary message devices" students should recognize that it's easier to invent a system of communication that uses combinations of binary signals with a simple device, rather than making a new, or increasingly complex device for each new problem. This lays the foundations for:
- Encoding complex information in computers using combinations of bits
- Developing clear communication protocols
- Binary Message Devices - Activity Guide in Large Print
- Binary Message Devices - Rubric in Large Print
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?
What is your personal definition of "information?" Take a minute to write it down.
- Think what "information" means to you. Explore how the definition changes depending on the context in which the word is used.
- It might be surprisingly difficult for students to define "information." If necessary you might modify the prompt and ask students to do word association by asking, "What other words come to mind when you hear the word: 'information'?"
- Landing on a correct definition of information is less important than thinking about the question, and realizing that "information" is a rich, multi-faceted word.
- The thinking process will set up the next several lessons, which are going to explore how information is sent between devices, and how it’s understood once it’s been sent.
- 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.
- 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.
Today we're going to work more with binary questions and messages. First you and your partner need to come up with a binary question.
Imagine that 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?
- You can choose to ask a "yes/no" question but you may have more fun choosing an "either/or" type question.
- Record some of the questions on the board or on another display. Assess whether they are indeed binary questions and correct any errors or misconceptions.
- The activity asks to go beyond representing only binary questions, so you might want to use examples that aren't simple true/false, yes/no type questions. A question like: "Coke or Pepsi?" could easily be expanded to include other options.
- You might think about it like a multiple choice test question, where for right now you only have two possible answers.
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.
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!
Challenge 1: Send a Binary Message
For the first challenge 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 - to your partner on the other side of the room.
You should try to make it fail-proof. Consider obstacles that might be thrown in your way. Would your device still work if:
- There was something in between you and your partner?
- You couldn’t see your partner?
- You were in a loud room?
- Your partner wasn’t paying attention?
Quick Share / Demonstration
- Ask teams to demonstrate how to use their device
- Go around the room to see the different kinds of things people came up with.
- We should start referring to these two states as state A and state B.
- Try to test and iteratively improve the designs as what appears to be "the end." Try to make your design better and better.
- Try to make your method of signaling as simple as possible.
- You might think to create devices that have a third "neutral" state or do-nothing state. Examine the device if it really only has two states.
- The point of this activity is NOT to learn the binary number system, but rather to understand that using physical devices that have binary states, we can send sequences of states to represent any number of things.
- As long as you come up with some kind of system for sending sequences of binary states - even if you don't map the classic binary number system - that is perfectly fine for now.
- The word for a single binary state is bit. In the curriculum you will see references to "bits" starting in the next lesson where the word is introduced. It could be introduced here if you like, it is up to you.
- While typically "bit" refers to a 0 or 1, for this lesson if you use the word "bit" you should use it to refer to states A and B to be consistent with the activity.
Binary Question: "Do we have a quiz or test today?"
- State A (Quick tug on the string) - means "quiz"
- State B (Two quick tugs on the string) - means "test"
Challenge 2: Four possible messages
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?
Quick Share / Demonstration / Discussion
- Demonstrate how to use the device
- Questions: Do we need to modify the device to add states? Can we use the device but just use it differently?
The purpose of the whole activity is to build toward an understanding that, from an engineering perspective, the simplest way to physically send an infinite number of messages over some distance is to make a binary message device, and to send unique sequences of binary states. This is how the internet at physical level actually works. After each little challenge the purpose of the demonstration and questions is to:
- Highlight different tactics for addressing the problem.
- Foreshadow the next challenge
There are 3 basic ways that we will focus on to make a device send 4 different messages:
- Modify the device so it can assume 4 different states.
- Similarly, we might just use the device differently in such a way that it can do 4 different things with it.
- Use the same representations of states A and B from your original device and come up with 4 unique sequences, for example A-A, A-B, B-A, B-B
Most of us will likely do the first two options - modify the device or use 4 different ways - but some might do the 3rd option at this point. Certainly, the preferred solution is number 3 and that's what we're working toward with the activity.
Note: For 4 messages the optimal solution is to use sequences of 2 binary messages (AA, AB, BA, BB). For 8 messages you can use sequences of 3 binary states (just add an A or a B to each of the previous 4 messages). For 16 messages, you can use a sequence of 4 binary messages and so on.
Challenge 3: Eight possible messages!
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.
Quick Share / Demonstration / Discussion
- Demonstrate how to use the device
- Questions: Do we need to modify their device to add states? Or can we not change the device but just use it differently?
Challenge 4: N-possible messages
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 many numbers
- Think back to your simple two-state device. Could you simply use it differently, rather than modifying it?
Topic for thought: How could we use our 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. Give students a few minutes to discuss and write.
- Could we use another group's device to send our set of messages? Why or why not? What would you need to know from the other groups?
- Based on what we've learned in today's activity what do we think are the limitations on the kinds of information we can send with binary messages?
1. Multiple Choice: A binary question is defined as:
- A. A piece of information that is sent in pairs
- B. Two questions which share the same answer
- C. A message which can be in two possible states
- D. A question which can be answered in only one of two possible ways
2. 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.
3. Modify your question so that it could be answered with a binary message. Explain why it can now be answered with a binary message.
4. 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?
5. 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.
- Switch devices with another group. Make sure you get their instructions for indicating state A and state B. Using their device, send your message to your partner. Why is this possible?
- What binary messaging systems are currently used in this room, school, or at home? How effective are they? Possible answers: Many kinds of alerts or notification systems are binary in nature: smoke detector, metal detector, some traffic signals, brake lights on cars, cell phone ringtones, etc. Similarly, vibrations can signal a variety of conditions based on length or number.
- What are the most important aspects of coordination when trying to send a single binary message from one place to another?
- What can’t be represented in a binary message?
- CSTA K-12 Computer Science Standards (2011): CL.L2:3, CL.L2:4
- CSTA K-12 Computer Science Standards (2011): CT.L2:7, CT.L2:8
- Computer Science Principles: 2.1.1 (A, B, C, E)
- Computer Science Principles: 2.1.2 (D, E, F)
- Computer Science Principles: 3.3.1 (A, B)