Primary Project
Worksheet 1
7-11's
Codes
What are codes?
Changing information from one type to another is known as encoding (or putting it into
code). You can encode a message as Semaphore using flags. In a way, the human voice
is encoded before we speak because the air we use changes as it passes through our
vocal cords.
Morse code
When the first electric telegraph systems were invented, sending words and sounds
along wires (like the telephone of today) was still a long way off. Samuel Morse was one
of the first people to change the alphabet people used every day into a code where
every letter of the alphabet was represented by a pattern of clicks as the electric
current was switched on and off (see Project 2, Worksheet 2).
Secrets and spies!
The Morse code telegraph was used across
the world and many people were trained
how to send (encode) and read (decode)
messages.
Organisations like the Army also began to
send telegraph messages. They wanted to
stop their enemies and rivals from reading
their communications, so secret codes were
devised which only few people knew about.
This is also known as encryption.
When radio was invented later on, the need
for secret codes was even greater
(especially in wartime) because radio signals
are very easy to overhear.
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Morse code being used by soldiers at war
Primary Project
Worksheet 1
7-11's
Cracking codes
Codes to crack
1. Here is a very simple code where each letter is represented by a number:
a. What does this message mean? 20 8 9 19
3 15 4 5
9 19
5 1 19 25
b. Write the numbers that represent the words TOP SECRET.
Creating codes
2. Make up your own secret code using the alphabet below. You could represent each
letter as:
λ
numbers or other letters
λ
shapes or patterns
λ
dots and dashes, like Morse code λ symbols.
3. Write a message in your code for a friend to crack. Make sure you give him/her a copy
of the code!
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