Name Date Period

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CS Unplugged activity

Secret Messages: Only Four Clues

About 20 minutesSoloPencil

No code chart this time. ASCII puts the letters and digits in order, so four codes are all you need to work out the rest. These messages use lowercase letters and digits too.

Your four clues

A = 65a = 970 = 48space = 32

What to do

1. Turn the hex code into decimal: first digit times 16, plus the second digit.
2. Pick the clue it belongs to: 48 to 57 is a digit, 65 to 90 a capital, 97 to 122 lowercase.
3. Subtract that clue’s number, then count forward that many places.
4. Write the character in the box under the code.

Now decode these

1. The first program most coders write prints this:

48

65

6C

6C

6F

20

77

6F

72

6C

64

2. You clicked a link to a page that isn't there. You see:

45

72

72

6F

72

20

34

30

34

3. In 1969 the first message sent over the early internet crashed after two letters. It said:

4C

6F

Answer key

1. Hello world
2. Error 404
3. Lo