1.2

Text, sound and images

Cambridge IGCSE Computer Science (0478)  · Unit 1: Data representation  · 10 flashcards

Text, sound and images is topic 1.2 in the Cambridge IGCSE Computer Science (0478) syllabus , positioned in Unit 1 — Data representation , alongside Number systems and Data storage and compression.  In one line: ASCII (American Standard Code for Information Interchange) is a character encoding standard for electronic communication. It represents text in computers, communication equipment, and other devices.

This topic is examined in Paper 1 (computer systems theory) and Paper 2 (algorithms, programming and logic).

The deck below contains 10 flashcards — 6 definitions and 4 key concepts — covering the precise wording mark schemes reward.  Use the 6 definition cards to lock down command-word answers (define, state), then move on to the concept and application cards to handle explain, describe and compare questions.

Key definition

The term 'ASCII' and provide an example of its use

ASCII (American Standard Code for Information Interchange) is a character encoding standard for electronic communication. It represents text in computers, communication equipment, and other devices.

Example: the ASCII code for the letter 'A' is 65.

What the Cambridge 0478 syllabus says

Official 2026-2028 spec

These are the exact learning objectives Cambridge sets for this topic. Match the command word (Describe, Explain, State, etc.) in your answer to score full marks.

  1. Understand Understand how and why a computer represents text and the use of character sets, including American standard code for information interchange (ASCII) and Unicode
  2. Understand Understand how and why a computer represents sound, including the effects of the sample rate and sample resolution
  3. Understand Understand how and why a computer represents an image, including the effects of the resolution and colour depth
Definition Flip

Define the term 'ASCII' and provide an example of its use.

Answer Flip

ASCII (American Standard Code for Information Interchange) is a character encoding standard for electronic communication. It represents text in computers, communication equipment, and other devices.

Example: the ASCII code for the letter 'A' is 65.
Key Concept Flip

What is the primary advantage of Unicode over ASCII?

Answer Flip

Unicode supports a significantly larger range of characters than ASCII, enabling it to represent text in various languages and scripts. This makes it more suitable for global communication and multilingual documents. It supports special symbols too.

Definition Flip

Explain the term 'pixel' in the context of digital images.

Answer Flip

A pixel is the smallest addressable element in a raster image (bitmap). It represents a single point of color, and the combination of many pixels creates the overall image. Higher pixel count generally means more detail.

Key Concept Flip

Describe the relationship between 'resolution' and image quality.

Answer Flip

Resolution refers to the number of pixels in an image, often expressed as width x height (

Example: 1920x1080). Higher resolution generally results in a clearer, more detailed image because it contains more pixels.
Definition Flip

What is 'colour depth' and how does it affect image quality?

Answer Flip

Colour depth, measured in bits, determines the number of colours a pixel can represent. Higher colour depth (

Example: 24-bit) allows for more colour variations, resulting in more realistic and vibrant images.
Definition Flip

What is a 'bitmap' image and how does it store image data?

Answer Flip

A bitmap is a raster graphic image file format that stores image data as a grid of pixels. Each pixel's color is individually stored, making bitmaps large files, especially for high resolutions and color depths.

Definition Flip

Explain the concept of 'sample rate' in digital audio.

Answer Flip

Sample rate refers to the number of audio samples taken per second when converting analog sound into digital data, measured in Hertz (Hz). A higher sample rate captures more audio information, resulting in better sound quality.

Definition Flip

Define 'bit depth' in the context of digital audio and its impact on audio quality.

Answer Flip

Bit depth (also known as audio resolution) refers to the number of bits used to represent each audio sample. A higher bit depth provides a greater dynamic range and lower noise, contributing to improved audio quality.

Key Concept Flip

Outline the factors that affect the file size of a digital image.

Answer Flip

The file size of a digital image is affected by resolution (number of pixels), colour depth (bits per pixel), and file format (

Example: bitmap vs. JPEG). Higher resolution and colour depth result in larger files.
Key Concept Flip

A digital audio file has a sample rate of 44.1 kHz and a bit depth of 16 bits. Explain what these values represent.

Answer Flip

A sample rate of 44.1 kHz means 44,100 audio samples are taken per second. A bit depth of 16 bits means each sample is represented using 16 bits, determining the dynamic range and accuracy of the audio.

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1.1 Number systems 1.3 Data storage and compression

Key Questions: Text, sound and images

Define the term 'ASCII' and provide an example of its use.

ASCII (American Standard Code for Information Interchange) is a character encoding standard for electronic communication. It represents text in computers, communication equipment, and other devices.

Example: the ASCII code for the letter 'A' is 65.
Explain the term 'pixel' in the context of digital images.

A pixel is the smallest addressable element in a raster image (bitmap). It represents a single point of color, and the combination of many pixels creates the overall image. Higher pixel count generally means more detail.

What is 'colour depth' and how does it affect image quality?

Colour depth, measured in bits, determines the number of colours a pixel can represent. Higher colour depth (

Example: 24-bit) allows for more colour variations, resulting in more realistic and vibrant images.
What is a 'bitmap' image and how does it store image data?

A bitmap is a raster graphic image file format that stores image data as a grid of pixels. Each pixel's color is individually stored, making bitmaps large files, especially for high resolutions and color depths.

Explain the concept of 'sample rate' in digital audio.

Sample rate refers to the number of audio samples taken per second when converting analog sound into digital data, measured in Hertz (Hz). A higher sample rate captures more audio information, resulting in better sound quality.

More topics in Unit 1 — Data representation

Text, sound and images sits alongside these Computer Science decks in the same syllabus unit. Each uses the same spaced-repetition system, so progress in one informs the next.

1.1 Number systems

10 flashcards
1.3 Data storage and compression

9 flashcards

Cambridge syllabus keywords to use in your answers

These are the official Cambridge 0478 terms tagged to this section. Mark schemes credit responses that use the exact term — weave them into your answers verbatim rather than paraphrasing.

ASCII Unicode character pixel resolution colour depth bitmap sample rate bit depth file size

Key terms covered in this Text, sound and images deck

Every term below is defined in the flashcards above. Use the list as a quick recall test before your exam — if you can't define one of these in your own words, flip back to that card.

The term 'ASCII' and provide an example of its use
Explain the term 'pixel' in the context of digital images
'colour depth' and how does it affect image quality
'bitmap' image and how does it store image data
Explain the concept of 'sample rate' in digital audio
'bit depth' in the context of digital audio and its impact on audio quality

How to study this Text, sound and images deck

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