These revision notes cover OCR GCSE Computer Science Paper 1 (J277/01) – Computer Systems for the 2025 exams.



All content is written in simple language to help GCSE students understand key theory topics clearly and revise efficiently.



Topics included:



System architecture (CPU, registers, fetch-execute cycle)



Memory and storage (RAM, ROM, secondary storage, cloud storage)



Data storage (binary, hexadecimal, images, sound, compression)



Computer networks, topologies, and protocol...