GCSE Computer Science: Data Representation Guide

Binary numbers

Computers store all data as binary (base 2), using only 0s and 1s. Each binary digit (bit) represents a power of 2, so converting between binary and denary (base 10) means adding up the place values of the 1s.

Hexadecimal

Hexadecimal (base 16) uses digits 0-9 and letters A-F, and is often used as a shorter, more readable way to represent binary values, such as colour codes or memory addresses — each hex digit represents exactly 4 binary bits.

Representing images and sound

Images are stored as a grid of pixels, each with a binary colour value; more bits per pixel (colour depth) means more possible colours but a larger file size. Sound is stored by sampling the sound wave at regular intervals (sample rate) and recording each sample's value (bit depth).

Units of data

Data size is measured in bits and bytes (8 bits), scaling up through kilobytes, megabytes, gigabytes and terabytes, each roughly 1000 times the size of the one before.

Common mistakes

• Losing track of place values when converting between binary and denary.
• Forgetting each hexadecimal digit maps to exactly 4 binary bits.
• Assuming higher resolution or sample rate has no cost — it means larger file sizes.