The first A-level year (ages 16–17) steps up from GCSE into the ideas that define computer science as a discipline: organising code with objects, choosing paradigms and writing it robustly, and building the abstract data structures — stacks, queues, trees, hash tables and graphs — that everything else stands on. Alongside that you meet how numbers really live in binary, how the CPU is wired and programmed at the level of registers and instructions, the Boolean algebra behind the logic, and the first big computational-thinking ideas. The topics below map the OCR/AQA-style A-level Computer Science specification; work each group in order.