1, 2, 3, code !  Cycle 3 activities  Lesson 1.4. How to encode and decode a binary message
Summary 
Continuing on from the previous lesson, students apply what they have learned to encode a short worded message in binary code, then decode a message in binary code they receive. 
Key ideas 
"Information"

Inquirybased methods 
Experimentation 
Equipment 
For each group 
Glossary 
List of elements, bit, binary code 
Duration 
1 hour 
Introductory question
The teacher reminds the students that they have received a message from the base that a storm is coming. The base team asked for information: the time rover will return to base.
Today, the students will code their reply in binary.
Activity: Encode a message for the base in binary (as a class, then in groups)
The teacher notes that the message the students must send to the base has only capital letters, spaces and periods (28 types of characters). They ask students to determine the smallest number of bits they need to encode each letter and suggest, if necessary, to look back at their notes from the previous lesson (Handout 30). The class agrees to limit coding to five bits per character.
The teacher hands out the top of Handout 31. They give students five minutes to create a correspondence between characters and fivebit combinations. During the group discussion, the class creates the following correspondence table:
5 bits  00000  00001  00010  00011  00100  00101  00110  00111 

Letter  A  B  C  D  E  F  G  H 
5 bits  01000  01001  01010  01011  01100  01101  01110  01111 
Letter  I  J  K  L  M  N  O  P 
5 bits  10000  10001  10010  10011  10100  10101  10110  10111 
Letter  Q  R  S  T  U  V  W  X 
5 bits  11000  11001  11010  11011  11100  11101  11110  11111 
Letter  Y  Z  point  Space  No meaning (these can be used for other punctuation signs if desired) 
The teacher tasks the student groups with using this correspondence table to encode the following text in binary:
TEN MINUTES
They hand out the middle section of Handout 31. The class gets:
Letter 
T 
E 
N 

M 
I 
N 
U 
T 
E 
S 
5bits group 
10011 
00100 
01101 
11011 
01100 
01000 
01101 
10100 
10011 
00100 
10010 
Challenge: Decoding a message sent by base (in pairs)
The teacher gives students the base's final reply (Handout 31) that the students must decode:
0111001010
Dividing the message into fivebit combinations gives students 01110 and 01010, which according to the table corresponds to the letters O and K. The message received from the base is "OK."
Individual exercise: Encoding and decoding binary messages.
The teacher gives the students 10 or 15 minutes to encode short messages and to pass them to fellow students to decode. Students enjoy this activity, which helps them consolidate what they learned in class.
Fourth Grade class, Carole Vinel, Paris
Conclusion
The class reviews the conclusion from the previous lesson, especially with regard to the following idea: binary code makes it possible to represent all types of data, especially texts.
Further study (unplugged)
To help students better understand why electronic instruments often require binary data representation, an analogy can be made using electric circuits that include the same number of light bulbs as the number of bits used for coding. Each bulb is linked to a switch. You can place each switch in an open/closed position (either 0/1 or OFF/ON). These are the only two states possible for a switch. For electronic devices, the electronic components are not light bulbs or switches, but they work in a similar way: they can be powered via electricity or not. It is practical to distinguish between these two states and coding information in binary.
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