Theory Topics & Mark Scheme Patterns

This lesson covers the key theory topics tested on AQA GCSE Computer Science Paper 2, with a focus on the specific methods, mark scheme expectations, and common errors for each topic. Understanding how AQA marks each topic will help you write answers that earn maximum marks.

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Data Representation: Binary, Hexadecimal, and Denary

Converting Between Number Systems

You must be able to convert fluently between binary (base 2), denary (base 10), and hexadecimal (base 16).

Binary to Denary

Use place values. An 8-bit binary number has the following columns:

128	64	32	16	8	4	2	1

Example: Convert 10110101 to denary.

128	64	32	16	8	4	2	1
1	0	1	1	0	1	0	1

128 + 32 + 16 + 4 + 1 = 181

Denary to Binary

Subtract the largest possible place value repeatedly.