⏱️ Do It Now
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Lesson 5 - Summer Term 1 - Representing Text
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📝 Do It Now |
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Answer each of the following: (1) What are the three small lights in a pixel called? (2) Explain what an audio sample is:
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Extension Question: Convert some hexadecimal numbers to denary with the converter app, and print screen your results below. Hexadecimal Conversion Practice
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🎯 Learning Objectives
- LO1: Describe what ASCII is and why it was developed
- LO2: Be able to decode and encode message between text and binary
📖 Everybody Reads
Data Representation So Far
So far, we have learned that computers store data using binary — patterns of 1s and 0s.
🔺We discovered how numbers can be represented in binary, and how humans often use hexadecimal to make long binary numbers shorter and easier to read.
🔺We also explored how images can be stored as binary by representing pixels with numbers, and how sound can be stored using binary sound samples.
Now, we will learn how computers store text characters such as letters, numbers, and symbols using binary 1s and 0s.
📝 Storing Text with ASCII
How Computers Store Characters
Computers cannot understand letters directly. Instead, each character is stored as a unique 8-bit binary number.
This system is called ASCII (American Standard Code for Information Interchange).
Each letter, number, symbol, or control code has its own binary value.
Because ASCII uses 8 bits, it can represent:
28 = 256 different characters
🔢 ASCII Character Ranges
What Are The ASCII Codes Used For?
- 0–31 → Control characters (instructions such as new line or tab)
- 32 → Space character
- 48–57 → Numbers 0–9
- 65–90 → Capital letters A–Z
- 97–122 → Lowercase letters a–z
- 123–255 → Extra symbols and extended characters
For example:(Character ➡️ Binary ➡️ Denary
- A = 01000001 = 65
- a = 01100001 = 97
- 5 = 00110101 = 53
💬 Example ASCII String
The Word "CAT"
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| C | A | T |
| 01000011 | 01000001 | 01010100 |
Each character is stored separately as its own 8-bit binary number.
💬 Another ASCII Example
The Word "hello"
🙋🏽♀️
| h | e | l | l | o |
| 01101000 | 01100101 | 01101100 | 01101100 | 01101111 |
Longer pieces of text are simply many ASCII characters stored one after another.
📝 Written Activity
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📝 Independent Activity (1) Questions:
🧩 ASCII Challenge (1)
Decode The Message Below
Convert each denary ASCII value into binary.
If your binary conversion is correct, the character will glow green and appear!
⚠️ ASCII Challenge (2)
Decode The Message Below
Convert each denary ASCII value into binary.
Correct answers will glow green and reveal the hidden message.
Do Your Own Encoding
Now you have translated a message with ASCII it is time to write your own message.
Click on This Link to write your own message
Remember to screenshot your message and paste it into OneNote
🕰️ Plenary
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📝 MWB Reflection Task |
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Open the mini-whiteboard app in a new tab Your teacher will start with these leading questions:
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🧮 Binary to Denary Helper
Click the 1s and 0s to turn bits on or off.
| 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 |
| 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |