Data Representation - SSS 1 Lesson Note

DATA REPRESENTATION

Subject: Digital Technologies
Class: SSS 1
Term: First Term
Week: 10
Topic: Data Representation
Duration: 80 Minutes (Double Period)

LEARNING OBJECTIVES

By the end of the lesson, students should be able to:

1. Explain the meaning of data representation in a computer system.
2. Define a bit and a byte.
3. Explain how text is represented using character codes.
4. Describe ASCII and state its common uses.
5. Explain Unicode and why it is important for representing characters from different writing systems.
6. Explain how digital images are represented using pixels and binary data.
7. Explain how sound is converted into digital form.
8. Differentiate between text, image and sound representation.

1. INTRODUCTION TO DATA REPRESENTATION

Computers process and store information electronically. Although users work with letters, numbers, pictures, sounds and videos, a computer ultimately represents digital information using binary values.

Definition: Data representation is the method used by a computer to encode, store, process and communicate data in a form that can be understood and handled by digital systems.

Digital devices represent information using combinations of 0 and 1. These two values are known as binary digits.

Example: A computer does not store the letter A, a photograph or a recorded voice in exactly the same physical form that humans see or hear. Each is converted into numerical/binary data so that the digital system can store and process it.

2. BITS AND BYTES

2.1 Bit

A bit is the smallest basic unit of digital information. The word bit is derived from binary digit.

A bit can have one of two possible values:

• 0
• 1

Binary values are used because digital electronic systems can represent two distinct states.

2.2 Byte

A byte is a group of eight bits.

1 Byte = 8 Bits

Bytes are commonly used as a basic unit for describing the storage requirements of data.

2.3 Larger Units of Digital Storage

Unit	Common Meaning
Bit	A single binary digit, 0 or 1.
Byte	8 bits.
Kilobyte (KB)	Approximately 1,000 bytes in decimal storage measurements.
Megabyte (MB)	Approximately 1,000 KB.
Gigabyte (GB)	Approximately 1,000 MB.
Terabyte (TB)	Approximately 1,000 GB.

Note: Storage manufacturers commonly use decimal units, while some computer systems and technical contexts use binary multiples such as KiB, MiB, GiB and TiB. Students should pay attention to the unit being used.

3. REPRESENTATION OF TEXT

Computers need a way to represent letters, numbers, punctuation marks and other characters. Character encoding systems assign numerical codes to characters.

For example, the letter A is assigned a particular numerical code in character encoding systems. The computer stores and processes that code in binary form.

Basic Idea:

Character → Character Code → Binary Representation

4. ASCII

ASCII stands for American Standard Code for Information Interchange.

ASCII is a character encoding standard originally developed for representing common English letters, numbers, punctuation marks and control characters in digital systems.

4.1 ASCII Representation

Standard ASCII uses 7 bits and provides codes for 128 characters. These include uppercase and lowercase English letters, digits, punctuation marks and control characters.

Character	Decimal ASCII Code
A	65
B	66
a	97
b	98
0	48
1	49

The numerical code is ultimately stored and processed in binary form by the computer.

5. UNICODE

Unicode is a character encoding standard designed to provide a consistent way of representing characters from many languages and writing systems.

Unlike the original ASCII set, which focuses mainly on common English characters and symbols, Unicode supports a much wider range of characters.

This makes Unicode important for international communication and for digital systems that need to display and process different languages.

5.1 Importance of Unicode

• Supports characters from many languages.
• Supports a wide range of symbols.
• Allows text from different writing systems to be represented digitally.
• Supports international websites, applications and digital documents.
• Helps reduce problems caused by incompatible character encodings.

6. ASCII AND UNICODE COMPARISON

Feature	ASCII	Unicode
Purpose	Represents a relatively small set of common characters.	Represents a very large range of characters from many writing systems.
Character coverage	Limited compared with Unicode.	Much broader.
Original standard	Standard ASCII uses 7 bits.	Uses several encoding forms, including UTF-8, UTF-16 and UTF-32.
Common use	English-oriented text and many basic computer systems.	Modern multilingual computing and digital communication.

7. REPRESENTATION OF IMAGES

Digital images are represented using tiny picture elements called pixels.

Pixel: A pixel is one of the smallest addressable elements of a digital image or display. A digital image consists of many pixels arranged in rows and columns.

Each pixel contains information about its colour or brightness. The computer stores this information as numerical data.

7.1 Image Resolution

Resolution refers to the amount of detail that can be represented in an image. It is commonly described using the number of pixels across the width and height of the image.

For example, an image with a resolution of 1920 × 1080 contains 1920 pixels across and 1080 pixels down.

7.2 Colour Representation

Colour images are commonly represented using combinations of colour components. One widely used model is RGB, which stands for:

• R – Red
• G – Green
• B – Blue

Different combinations and intensities of these components can represent a wide range of colours.

7.3 Image File Size

The amount of data required to store an image depends on factors such as its dimensions, colour depth and compression method.

Remember: Higher image resolution and greater colour detail can require more storage space, although compression can reduce the size of an image file.

8. REPRESENTATION OF SOUND

Sound is naturally an analogue phenomenon. Computers, however, process digital data. Therefore, sound must be converted from analogue form into digital data before a computer can store and process it digitally.

8.1 Sampling

Sampling is the process of measuring the amplitude of a sound wave at regular intervals.

Each measurement is converted into a numerical value that can be represented digitally.

8.2 Sample Rate

The sample rate is the number of samples taken per second. It is usually measured in hertz (Hz) or kilohertz (kHz).

For example, a sample rate of 44.1 kHz means that 44,100 samples are taken per second.

8.3 Bit Depth

Bit depth refers to the number of bits used to represent each audio sample.

A higher bit depth allows more possible numerical values to represent the amplitude of each sample and can provide greater potential detail in the digital recording.

8.4 Digital Audio File Size

The amount of storage required for digital audio is influenced by factors such as:

• Sample rate
• Bit depth
• Number of audio channels
• Duration of the recording
• Compression method

9. TEXT, IMAGE AND SOUND REPRESENTATION

Data Type	How It Is Represented	Important Concepts
Text	Characters are assigned numerical codes and stored digitally.	ASCII, Unicode, character encoding
Image	Images are represented using pixels and numerical colour/brightness information.	Pixels, resolution, colour depth, RGB
Sound	Sound waves are sampled and converted into numerical values.	Sampling, sample rate, bit depth

10. IMPORTANCE OF DATA REPRESENTATION

Data representation is important because it allows different forms of information to be stored, processed and transmitted by digital devices.

Its importance includes:

1. Allows computers to process different types of data.
2. Makes it possible to store information digitally.
3. Supports communication between digital devices.
4. Allows text to be displayed in different languages.
5. Allows images to be stored and displayed.
6. Allows sound to be recorded, stored and played digitally.
7. Provides a common way for digital systems to process information.

11. CLASS ACTIVITY

Activity 1: Convert the decimal values 5, 10 and 15 into binary.

Activity 2: Students should identify the difference between ASCII and Unicode.

Activity 3: Students should identify the pixels, resolution and colour information involved in a digital image.

Activity 4: Students should explain what happens when a microphone records a sound for storage on a computer.

12. SUMMARY

Data representation is the way digital systems encode, store and process information. Computers represent digital information using binary values made up of 0s and 1s.

A bit is a single binary digit, while a byte consists of eight bits. Text is represented using character encoding systems such as ASCII and Unicode. ASCII provides a relatively limited set of characters, while Unicode supports a much wider range of characters and writing systems.

Digital images are represented using pixels and numerical colour information. Digital sound is produced by sampling analogue sound waves and converting the samples into numerical data. Sample rate and bit depth are important characteristics of digital audio.

13. EVALUATION

1. What is data representation?
2. Define a bit and a byte.
3. How many bits make one byte?
4. What does ASCII stand for?
5. State two differences between ASCII and Unicode.
6. Why is Unicode important in modern digital communication?
7. What is a pixel?
8. Explain how digital images are represented in a computer.
9. What is sampling in digital sound?
10. State three factors that can affect the size of a digital audio file.

14. ASSIGNMENT

1. Explain the meaning of data representation and describe why it is important in digital technology.
2. Define bit and byte and explain the relationship between them.
3. Explain ASCII and Unicode and state three differences between them.
4. Explain how a digital image is represented using pixels.
5. Explain how analogue sound is converted into digital form.
6. Explain the meaning of sample rate and bit depth in digital audio.

15. QUICK QUIZ

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1. How many bits make one byte?

A. 4 B. 8 C. 16 D. 32

2. What does ASCII stand for?

A. American Standard Code for Information Interchange B. American System for Computer Information Input C. Automated Standard Code for Internet Information D. Advanced System Code for Information Integration

3. Which character encoding system supports a very large range of writing systems?

A. ASCII B. Unicode C. RGB D. JPEG

4. What is a pixel?

A. A unit used to measure sound B. A character encoding system C. A small element of a digital image D. A type of computer processor

5. What is sampling in digital audio?

A. Measuring a sound wave at regular intervals B. Printing an audio file C. Compressing a picture D. Converting text into an image

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