OCR J277

GCSE Computer Science

Everything on the OCR J277 specification, written as a route to a grade 9. Every topic has a full explanation, key terms, a ten question knowledge check and five auto marked exam-style questions with real mark schemes.

Start the first topic Practice papers Printable worksheets

25Topics

250Quiz questions

466Exam marks

Grade 9Target grade

Your route to Grade 9

Revision works when it has an order. Follow these stages rather than opening topics at random.

Learn it properly the first time

Do not skim. Read one topic slowly, close the page, and write down what you remember. The gap between what you read and what you can recall is the only thing that matters, and you can only see it by testing yourself.

Pass every knowledge check at 100 per cent

Ten questions per topic. Anything below full marks means go back to that section. Getting 7 out of 10 and moving on is how students end up with a grade 5 while feeling like they revised.

Write the exam answers from memory

Five written questions per topic, marked against the real mark scheme. Write the answer first, then compare. Reading a model answer teaches you almost nothing until you have tried to produce one yourself.

Space it out and come back

Return to each topic after three days, then after two weeks. Redo only the quiz. Spaced retrieval is the single most effective revision method there is, and it takes ten minutes per topic.

Sit full papers against the clock

Knowing the content is not the same as scoring under time pressure. Do complete papers in 1 hour 30 minutes with no notes, mark them honestly, and keep a list of every mark you dropped.

Close the gaps you actually have

Your mistakes list is your revision plan. Grade 9 students are not the ones who know everything, they are the ones who found out what they did not know and fixed it before May.

Paper 1 3 topics

1.1 Systems Architecture

How the processor works, what makes one faster than another, and why the computer inside a washing machine is built differently.

1.1.1Architecture of the CPUWhat the processor is actually for, the job of every component inside it, and the fetch decode execute cycle written the way examiners want to read it.1.1.2CPU PerformanceThe three factors that decide how fast a processor is, why doubling the cores does not double the speed, and how to compare two CPUs in an exam answer.1.1.3Embedded SystemsWhat an embedded system is, how it differs from a general purpose computer, and why your washing machine does exactly one job extremely reliably.

Paper 1 8 topics

1.2 Memory and Storage

RAM, ROM, virtual memory and secondary storage, then every kind of data represented in binary and how it is compressed.

1.2.1Primary Storage: RAM, ROM and Virtual MemoryWhy the computer needs memory at all, the real difference between RAM and ROM, and what virtual memory is actually doing when your machine slows to a crawl.1.2.2Secondary StorageWhy every computer needs secondary storage, the three technology types, and how to choose the right device using the six characteristics examiners expect.1.2.3Units of DataBits, nibbles and bytes through to petabytes, why computers use binary at all, and how to answer file size calculation questions without losing marks on the units.1.2.4Binary, Denary and HexadecimalConverting between all three number bases with a method that does not fail under pressure, binary addition including overflow, and binary shifts with their effect on the value.1.2.4Storing Characters: ASCII and UnicodeHow text becomes binary, why ASCII was not enough, and the exact trade off between ASCII and Unicode that examiners ask about every year.1.2.4Storing ImagesHow a picture becomes binary, what resolution and colour depth actually control, and the file size calculation with metadata included.1.2.4Storing SoundHow a continuous analogue wave becomes a list of binary numbers, what sample rate and bit depth each control, and the sound file size calculation.1.2.5CompressionWhy files are compressed at all, exactly how lossy and lossless differ, and how to choose correctly between them in any scenario the exam gives you.

Paper 1 2 topics

1.3 Computer Networks, Connections and Protocols

How computers are joined together, the hardware that does it, and the protocols that let them understand each other.

1.3.1Networks and TopologiesLANs and WANs, the hardware that makes a network work, client server against peer to peer, star against mesh, and the factors that decide how fast it all runs.1.3.2Wired and Wireless Networks, Protocols and LayersWi-Fi against Ethernet, IP and MAC addressing, every protocol on the specification with what it actually does, and why layering makes the internet possible.

Paper 1 1 topics

1.4 Network Security

Every form of attack on the specification, how each one works, and the defence that actually stops it.

1.4Network Security: Threats and PreventionEvery threat on the specification explained by how it actually works, every prevention method, and the reason the biggest weakness in any network is a person.

Paper 1 1 topics

1.5 Systems Software

What the operating system does all day, and the utility programs that keep a computer healthy.

1.5Systems SoftwareWhat the operating system is really doing while you use a computer, all five of its management jobs, and every utility program on the specification.

Paper 1 1 topics

1.6 Ethical, Legal, Cultural and Environmental Impacts

The four impact categories, the four acts you must name, and how to structure the eight mark answer so it reaches the top level.

1.6Ethical, Legal, Cultural and Environmental ImpactsThe four impact categories, all four pieces of legislation you must name, open source against proprietary software, and how to structure the eight mark essay so it actually scores.

Paper 2 3 topics

2.1 Algorithms

Computational thinking, designing and tracing algorithms, and the five searching and sorting algorithms you must be able to trace.

2.1.1Computational ThinkingAbstraction, decomposition and algorithmic thinking, explained with examples that actually show what each one does rather than just naming it.2.1.2Designing, Creating and Refining AlgorithmsPseudocode, flowcharts, trace tables and finding errors in someone else's algorithm, which is the skill Paper 2 tests most heavily.2.1.3Searching and Sorting AlgorithmsLinear and binary search, bubble, merge and insertion sort. How each one works step by step, and exactly when to choose which.

Paper 2 3 topics

2.2 Programming Fundamentals

The three constructs, data types and casting, then strings, arrays, files, SQL and subroutines.

2.2.1Programming FundamentalsVariables, constants, the three programming constructs, operators and how to write code that an examiner can follow and award marks to.2.2.2Data Types and CastingThe five data types you must know, why choosing the right one saves memory, and why casting is the fix for the most common bug in beginner programs.2.2.3Additional Programming TechniquesStrings, arrays, file handling, SQL, subroutines and random numbers. This is the widest single topic on Paper 2 and the one with the most easy marks available.

Paper 2 1 topics

2.3 Producing Robust Programs

Defensive design, validation, authentication, maintainability and test plans that find real faults.

2.3Producing Robust ProgramsDefensive design, validation, authentication, maintainability, and how to design a test plan that actually finds the bugs rather than confirming what you already believe.

Paper 2 1 topics

2.4 Boolean Logic

AND, OR and NOT, logic diagrams and truth tables done in a way that does not go wrong under pressure.

2.4Boolean LogicAND, OR and NOT gates, drawing and reading logic diagrams, and completing truth tables for combined circuits without making arithmetic slips.

Paper 2 1 topics

2.5 Programming Languages and IDEs

High and low level languages, compilers against interpreters, and the features of an IDE.

2.5Programming Languages and IDEsHigh and low level languages, translators and the exact difference between a compiler and an interpreter, plus the four IDE features you must name.