On your own, look at the list of number pairs below.
| 1 | 1 |
| 2 | 14 |
| 7 | 4 |
| 10 | 31 |
What do you think this list represents? Once you have an idea, come up with another item that belongs on the list, and be ready to explain why.
For this activity, get into pairs. You'll need a way to send short messages back and forth without talking.
Look at the samples below. Using only numbers, you will need to communicate messages like these to your partner. No letters or other characters allowed, just numbers!
Together, come up with a system that will let you do this.
Before we start sending real messages, each pair briefly explain the system you came up with. What does each number mean?
Come up front to find out the message you'll need to send. Using your system, send it to your partner.
Figure out what the message says. You'll need to tell me what it said.
Each pair, explain your system: how did you turn the message into numbers, and how did your partner turn the numbers back into words?
Make sure your message matches this exactly, including capitalization and spacing.
Take a minute with your partner to update your system if you need to.
Figure out what the message says. You'll need to tell me what it said.
Come up front to find out the message you'll need to send. Using your system, send it to your partner.
Each pair, explain your system: how did you turn the message into numbers, and how did your partner turn the numbers back into words?
Make sure your message matches this exactly, including the punctuation.
Take a minute with your partner to update your system if you need to.
Come up front to find out the message you'll need to send. Using your system, send it to your partner.
Figure out what the message says. You'll need to tell me what it said.
Each pair, explain your system: how did you turn the message into numbers, and how did your partner turn the numbers back into words?
Make sure your message matches this exactly, including capitalization, punctuation, and spacing.
Take a minute with your partner to update your system if you need to.
Figure out what the message says. You'll need to tell me what it said.
Check the chat for the message you need to send. Using your system, send it to your partner.
Each pair, explain your system: how did you turn the message into numbers, and how did your partner turn the numbers back into words?
Make sure your message matches this exactly, including capitalization, punctuation, and spacing.
Nice work. You just built your own system for representing text with numbers.
How many bits would you need to send one character in your message? How do you know?
Hint: What is the largest number your system uses? How many bits would it take to represent that number?
Let's call the number of bits it takes to send one character a byte. How many bytes would it take to send a message like this one?
Computers assign a number to every letter, digit, and symbol on a keyboard, plus a handful of control characters that don't print anything at all. Control characters are instructions like move over one space or move to the next line.
Every time you press Tab or Enter, you're sending one of these numbers.
This numbering system is called ASCII (pronounced "ask-ee").
Take an ordinary text message.
We don't have to think about these layers when we send a text message, but every message is really just zeros and ones underneath.
Recall: how did you make sure your partner knew where one number ended and the next began?
On your whiteboards, you had gaps between your numbers. A computer's bit stream doesn't. It's just one long line of 0s and 1s with no spaces at all.
So how does the computer know where h ends and o begins?
Everyone agrees ahead of time: every character is exactly 8 bits, one byte. Count off eight bits, and you've found the next character, no gaps required.