OCR GCSE Computer Science Revision

Explore OCR GCSE Computer Science revision topics. Check the official specification for complete requirements for your exam year and route.

Qualification code: J277

11 topic groups · 26 numbered specification points · 37 checklist items

Official OCR course and specification (opens in a new tab)

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Computer Science topic list

This checklist follows the linked J277 specification's assessed content. Check the official document for assessment details, updates and your exam year.

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Systems architecture
- 1.1.1 Architecture of the CPU: CPU purpose and fetch–execute cycle; ALU, control unit, cache and registers; Von Neumann registers (MAR, MDR, program counter and accumulator), their roles in the cycle and the distinction between stored data and addresses.
- 1.1.2 CPU performance: how clock speed, cache size and core count, separately and in combination, affect system performance.
- 1.1.3 Embedded systems: their purpose, definition and typical characteristics, with familiarity with a range of examples.
Memory and storage
- 1.2.1 Primary storage (memory): why it is needed; RAM and ROM purposes and characteristics; cache; why virtual memory may be needed and how data moves between RAM and secondary storage when RAM is full.
- 1.2.2 Secondary storage: why it is needed; optical, magnetic and solid-state media; recognising and comparing devices/media and choosing suitable storage in context by capacity, speed, portability, durability, reliability and cost.
- 1.2.3 Units: binary storage units (bit, 4-bit nibble, 8-bit byte, KB, MB, GB, TB and PB using the stated decimal conversions); why data is represented in binary; fixed device capacities; calculating file and total storage sizes, including sound (sample rate × duration × bit depth), images (colour depth × height × width) and text (bits per character × character count). 1,024-based conversions and allowance for metadata are acceptable.
- 1.2.4 Data storage: convert positive denary whole numbers (0–255), binary (1–8 bits) and two-digit hexadecimal (00–FF) between bases; add binary integers up to 8 bits and explain overflow; identify most/least significant bits; perform and explain left/right binary shifts; represent characters with binary character sets (including ASCII and Unicode), relating bits per character to the number and ordering of characters; represent images as coded pixels and explain how colour depth, resolution and metadata affect file quality and size; sample analogue sound into binary and explain how sample rate, duration and bit depth affect playback and file size.
- 1.2.5 Compression: why compression is needed; lossy and lossless methods, common use scenarios, their effects on files, and the advantages and disadvantages of each.
Computer networks, connections and protocols
- 1.3.1 Networks and topologies: LANs and WANs, their characteristics and examples; factors such as connected-device count and bandwidth; client–server and peer-to-peer roles; LAN hardware (wireless access points, routers, switches, NICs and transmission media) and its tasks; the Internet as interconnected networks; DNS and URL-to-IP resolution; hosting, web servers and clients; cloud services and their advantages/disadvantages; star and mesh topologies and their advantages/disadvantages; apply network knowledge to scenarios.
- 1.3.2 Wired and wireless networks, protocols and layers: Ethernet, Wi-Fi and Bluetooth connection modes; compare and recommend wired/wireless connections; encryption's role in protecting network data; IPv4/IPv6 address formats and MAC-address assignment, format and network use; standards as interoperability rules; communication protocols as transfer rules and the purposes/key features of TCP/IP, HTTP, HTTPS, FTP, POP, IMAP and SMTP; protocol layers and their benefits (with the four-layer TCP/IP model as an example).
Network security
- 1.4.1 Threats to computer systems and networks: malware, social engineering (including phishing and exploiting people as a weak point), brute-force attacks, denial-of-service attacks, data interception/theft and SQL injection; understand how each attack is used and its purpose and the threats it poses.
- 1.4.2 Identifying and preventing vulnerabilities: penetration testing, anti-malware, firewalls, user access levels, passwords, encryption and physical security; understand the vulnerabilities or attacks each method can limit and how it does so.
Systems software
- 1.5.1 Operating systems: purpose and functions of user interfaces, memory management/multitasking, peripheral management and drivers, user management, and file management; interface features; memory transfer and allocation to applications and how this supports multitasking; managing device-to-processor data transfer; accounts, access rights and security; file naming, folders, moving and saving.
- 1.5.2 Utility software: its housekeeping purpose and role in tasks beyond the operating system; the purpose and need for encryption, defragmentation and data-compression utilities.
Ethical, legal, cultural and environmental impacts of digital technology
- 1.6.1 Ethical, legal, cultural and environmental impact: privacy and other wider societal effects of digital technology; use varied examples to discuss impacts. Relevant law: Data Protection Act 2018, Computer Misuse Act 1990 and Copyright, Designs and Patents Act 1988, including each law's purpose and permitted/prohibited actions. Software licensing: why licences are needed; open-source access to and modification of source code versus proprietary software without source access (commonly off-the-shelf); recommend a licence for a scenario and weigh benefits and drawbacks.
Algorithms
- 2.1.1 Computational thinking: abstraction, decomposition and algorithmic thinking, and using these principles to define and refine problems.
- 2.1.2 Designing, creating and refining algorithms: identify a problem's inputs, processes and outputs; use structure diagrams to show a problem's structure and linked subsections; create, interpret, correct, complete and refine algorithms in pseudocode, flowcharts or a reference/high-level language; identify syntax and logic errors and suggest corrections; trace algorithms with trace tables; use nested selection and iteration.
- 2.1.3 Searching and sorting algorithms: linear and binary search, and bubble, merge and insertion sort; understand each algorithm's main steps, code segments and prerequisites, apply it to data, and recognise it from code, pseudocode or OCR Exam Reference Language.
Programming fundamentals
- 2.2.1 Programming fundamentals: variables, constants, operators, input/output and assignment; sequence, selection and count- or condition-controlled iteration; Boolean AND, OR and NOT; comparison operators (==, !=, <, <=, >, >=) and arithmetic operators (addition, subtraction, multiplication, division, MOD, DIV and exponentiation); practical use of these techniques in a high-level language.
- 2.2.2 Data types: integer, real, Boolean, character and string; choose appropriate types for a scenario and use casting to change a type temporarily where useful.
- 2.2.3 Additional programming techniques: string concatenation and slicing; file open/read/write/close operations; records; SQL searching with SELECT, FROM and WHERE; 1D and 2D arrays (including 2D arrays representing database tables of fields and records); structured subprograms using functions and procedures, when to use each, and local/global variables and constants and passing/returning arrays; generate and use random numbers.
Producing robust programs
- 2.3.1 Defensive design: anticipate misuse; authenticate users; validate input and handle invalid data; maintainable program structure through subprograms, naming conventions, indentation and appropriate comments; practical design of validation and simple username/password authentication.
- 2.3.2 Testing: purpose and iterative versus final/terminal testing; identify syntax errors that prevent translation/execution and logic errors that produce unexpected output; select normal, boundary, invalid (correct type but rejected) and erroneous (wrong type and rejected) test data for scenarios; create or complete test plans and refine algorithms.
Boolean logic
- 2.4.1 Boolean logic: AND, OR and NOT operators and gate symbols; each gate's truth table; create, complete and edit logic diagrams and truth tables for scenarios, combine operators and work with multiple gates to solve problems.
Programming languages and Integrated Development Environments
- 2.5.1 Languages: characteristics and purposes of high- and low-level languages; why translators are needed; compiler and interpreter characteristics and their differences, benefits and drawbacks.
- 2.5.2 The Integrated Development Environment (IDE): editors, error diagnostics, run-time environments and translators; what these tools provide and how they support program development, with practical experience of a range of tools in at least one IDE.

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