Unit Overview
Information representation
CIE A-Level Computer ScienceΒ· 5 min read π n/a
1. Unit at a glance
This unit follows a logical, progressive learning arc: we start with core number system concepts, then move to encoding for different data types, and end with techniques to reduce data size for storage and transmission. The core theme here is simple: all data that computers process is ultimately just sequences of 0s and 1s.
Each sub-topic builds directly on the previous one: understanding number bases is required to work with binary integer representation, which in turn supports understanding real number and multimedia encoding. Mastering these fundamentals will make every other topic in the course easier.
Below are all sub-topics in this unit:
Number bases
Learn to convert between binary, decimal, and hexadecimal number systems.
β β β± 10 min
Binary representation of integers
Explore unsigned, two's complement, and binary arithmetic for whole numbers.
β β β± 12 min
Binary representation of real numbers
Understand fixed-point and floating-point binary for non-integer values.
β β β β± 15 min
Character encoding
Learn how text is encoded using standards like ASCII and Unicode.
β β± 8 min
Binary representation of images
Understand bitmaps, resolution, colour depth, and calculate image file size.
β β β± 10 min
Binary representation of sound
Learn how analogue sound is digitised and calculate audio file size.
β β β± 10 min
Data compression
Compare lossy and lossless compression and their practical applications.
β β β± 9 min
2. Common Pitfalls
Wrong move:
Confusing colour depth for images with sample rate for sound
Why:
Mixing up these parameters leads to frequent errors in file size calculations
Correct move:
Remember: bit/colour depth describes bits per sample/pixel; sample rate only applies to audio sampling frequency
Wrong move:
Assuming all real numbers can be stored exactly as binary floating-point
Why:
Students often forget that limited bit size creates rounding errors for many values
Correct move:
Recognise that floating-point binary only stores approximations of most real numbers
Wrong move:
Converting hexadecimal to decimal first when converting to binary
Why:
This extra step introduces unnecessary calculation errors
Correct move:
Convert each hex digit directly to a 4-bit binary sequence for fast, accurate conversion
3. Quick Reference Cheatsheet
Concept / Formula | Description |
|---|---|
Image file size | |
Sound file size | |
1 byte | 8 bits |
Two's complement negative | Flip all bits, add 1 to the result |
Hex to binary | 1 hex digit = 4 binary digits |
Lossless compression | Original 100% of data can be reconstructed |
Lossy compression | Permanently removes data to achieve much smaller file sizes |
What's Next
We recommend working through the sub-topics in order, as each builds on concepts from the previous topics. Start with the first sub-topic, Number Bases, to master the core fundamentals needed for all later topics in this unit. Once you complete all sub-topics here, you can move on to the next core unit for CIE 9618: Communication and Internet Technologies.