OCR A-Level Computer Science Active Recall Guide (H446)
OCR · A-Level
OCR A-Level Computer Science Active Recall Guide
Every topic of specification H446 written as exam-style questions with the answers printed after them. 1,549 questions across 16 topics and 116 subtopics, covering both written components from processor architecture to the standard algorithms.
- OCR
- A-Level
- Specification H446
- 1,549 questions
Guide overview All 16 topics Sample questions Papers and weighting Look inside Questions and answers
What the exam asks of you
OCR A-Level Computer Science is assessed by two written papers and a programming project. Computer Systems and Algorithms and Programming are 2 hours 30 minutes and 140 marks each, worth 40 per cent apiece. The programming project is marked by your centre and moderated by OCR, and carries the remaining 20 per cent.
The two written papers between them carry 80 per cent of the grade and almost all of that is recall of precise definitions, structures and procedures. Knowing roughly what a cache does, or roughly how a merge sort works, scores nothing.
| Paper | Covers | Length | Marks | Weighting |
|---|---|---|---|---|
|
Component 01 Computer systems |
The structure and function of the processor, and input, output and storage Systems software, applications generation, software development and types of programming language Exchanging data, networks, web technologies, data types and data structures Boolean algebra, and the legal, moral, cultural and ethical issues |
2 hours 30 minutes | 140 marks | 40% |
|
Component 02 Algorithms and programming |
Elements of computational thinking: thinking abstractly, ahead, procedurally, logically and concurrently Problem solving and programming, including programming techniques and computational methods Algorithms: searching, sorting, path finding and the analysis of complexity |
2 hours 30 minutes | 140 marks | 40% |
|
Component 03 or 04 (80 if carried forward) Programming project |
A computing problem chosen by the teacher or learner, analysed, designed, developed, tested and evaluated Assesses the practical application of the content of both written papers Marked by the centre and moderated by OCR, as an upload (03) or by post (04), or carried forward (80) on a retake |
Non-exam assessment | 70 marks | 20% |
What is in the guide
All 16 topics
Every topic has its own page with its subtopics, what it covers and sample questions.
Sample questions
Taken from the guide. Answer each one closed book first, then open the answer.
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Inside the CPU: ALU, control unit, registers and buses
What is held in the current instruction register, and what two parts does it split into?
Show the answer
The CIR holds the instruction currently being decoded and executed, copied there from the MDR at the end of the fetch. The control unit splits it into the opcode, which says what operation to perform, and the operand, which says what to perform it on: a value, a register, or a memory address. -
Operating systems: need, function and purpose
How does an operating system provide a 'platform' for application software?
Show the answer
It exposes a consistent set of services and interfaces (often called an application programming interface) that applications call instead of controlling hardware. A word processor asks the operating system to save a file; it does not need to know whether the storage is a hard disk drive, a solid state drive or a network share. -
Applications and utilities
What is application software?
Show the answer
Software that carries out a task the end user actually wants done, rather than running or maintaining the computer itself - for example a word processor, a spreadsheet, a web browser, a database front end, a photo editor or a game. It relies on system software to reach the hardware. -
The five development methodologies
State the stages of the waterfall lifecycle in order.
Show the answer
Feasibility study; requirements analysis; design; implementation (coding); testing; installation, then ongoing evaluation and maintenance. Each stage is completed and approved before the next begins. -
Programming paradigms and procedural languages
What is a programming paradigm?
Show the answer
A style or approach to programming - a whole way of thinking about how a program should be organised and what a program fundamentally is. It determines how the problem is broken down, how data and instructions are represented and how the flow of the program is controlled, rather than merely which keywords are typed. -
Compression
Lossy compression generally produces much smaller files than lossless. Why, then, is lossless ever used?
Show the answer
Because for many kinds of data any loss at all destroys the file's meaning. Lossless is used whenever the exact original bits are needed, and the price of that guarantee is a smaller reduction in size. Lossy is only acceptable where an approximation is good enough for the human viewer or listener. -
Characteristics of networks, LANs and WANs, protocols and standards
Is the internet a LAN or a WAN?
Show the answer
The internet is the largest example of a wide area network - in fact a global collection of interconnected wide area networks. It spans the whole planet, no single organisation owns its infrastructure, and it exists to join together enormous numbers of separate networks including individual LANs.
How the guide is worked
Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.
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Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
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Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
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Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.
Read the full method, the return schedule and the research behind it.
Look inside
Questions for a subtopic print together and the answers for that section print after them.
- Processors: Structure, Performance and Types91
- Input, Output and Storage46
- Systems Software97
- Applications Generation64
- Software Development41
- Types of Programming Language64
- Exchanging Data122
- Networks92
- Web Technologies71
- Data Types and Number Representation152
- Data Structures124
- Boolean Algebra85
- and 4 more
- How should you decide which input device suits a particular problem?
- Which input device suits a supermarket checkout, and why?
- A national testing organisation must mark twenty thousand multiple choice answer sheets. What input device, and what limitation does it have?
- A company wants to turn a filing cabinet of printed letters into searchable text. Which devices and techniques?
- Why is a touchscreen the right input device for a self-service ticket machine at a railway station?
- Which input device would you specify for a professional digital illustrator?
- What input options exist for a user who cannot use their hands?
- Describe suitable output devices for a blind user.
- Which type of printer for which job?
- Match the characteristics of the device to the demands of the problem: how much data must be entered and how quickly, how accurate the entry has to be, the physical environment the device will live in, who the users are and what they can physically do, the cost and durability required, and what form the data is already in. A good justification always names the property of the device and links it to a stated requirement of the problem.
- A barcode scanner. A laser or camera reads the pattern of bars and spaces, which is far quicker than typing a product code and removes typing errors entirely; the code is already printed on the goods so nothing has to be prepared; the scanners are cheap and hard-wearing enough for constant use. The till uses the code to look up the price and update the stock count automatically. A keypad is still needed as a fallback for damaged barcodes and for loose items.
- Optical mark recognition. The reader detects the position of pencil marks in pre-printed boxes on the form, processing thousands of sheets an hour with almost no errors and no operator typing anything. The limitation is that it only works with specially designed forms, marks must be in the right place and made with the right kind of pencil, and it reads only the presence of a mark, not any handwriting.
- A sheet-feed or flatbed scanner to capture each page as an image, followed by optical character recognition software to convert the shapes of the printed characters into character codes. Scanning alone gives only a picture, which cannot be searched or edited; OCR is what makes the text usable. Accuracy depends on the quality of the print, and OCR output has to be checked, unlike optical mark recognition which is essentially exact.
- It combines the display and the input in one sealed unit, so there is no separate keyboard or mouse to be stolen, vandalised or damaged by weather; it tolerates dirt and wet hands; it needs no training, because the user simply touches what they can see; and the controls can be redrawn at every step to show only the choices that are currently relevant. Its weaknesses are that it is slow for entering long text and that an alternative must be offered for users who cannot see or reach the screen.
- A graphics tablet with a pressure-sensitive stylus. Pressure and tilt are captured as well as position, so the software can vary line width and opacity as a real brush would; the absolute positioning and high resolution give far finer control than a mouse, which reports only relative movement. The illustrator draws with a hand movement they already have years of practice in.
- Speech recognition through a microphone, for both dictation and commands, which is fast but needs a quiet environment and reliable speech. Eye-tracking or head-tracking to move a pointer, selecting by dwelling on a target. A single switch operated by any reliable movement, combined with on-screen scanning that highlights each option in turn. The choice depends on which movements the user has available, how much text they need to enter and how noisy or public the setting is.
- A screen reader converting on-screen text to synthesised speech through speakers or headphones, which is quick for reading prose and needs no extra hardware. A refreshable braille display, which raises and lowers pins to form a line of braille cells that the user reads by touch, and which is far better for anything where exact characters matter, such as programming, spelling or numerical data. Many users combine both. Tactile or embossed printouts can be produced for diagrams.
- A laser printer for high volume office documents: it is fast, cheap per page and gives sharp text, using a laser to write a charged image on a drum which picks up toner and fuses it to the paper with heat. An inkjet for occasional colour photographs, since it blends colours well on photo paper and the machine is cheap, though the ink is expensive per page. A 3D printer to make a physical prototype, building the object up in thin layers of deposited material. A large-format plotter for architectural and engineering drawings that must stay accurate at full size.
questions
Scroll sideways to turn through the pages.
Questions students ask first
Does it cover the programming project?
No. Components 03 and 04 are the programming project, marked by your centre and moderated by OCR. It is a piece of coursework rather than examined content, so there is nothing to recall.
The guide covers the two written papers, which are 80 per cent of the grade between them.
Does it cover both written components?
Yes. 13 topics for Component 01, Computer Systems, and 3 for Component 02, Algorithms and Programming. The full topic list is here.
Which language does it assume?
None. OCR examines pseudocode on the written papers, and the guide follows that: the questions ask what a construct does, what an algorithm’s steps are and what its complexity is, rather than the syntax of a particular language. Your project language is your own choice and does not change any of this.
Are the standard algorithms in it?
Yes, with 230 questions on Algorithms alone: linear and binary search, bubble, insertion, merge and quick sort, Dijkstra and A*, breadth and depth first traversal, stack, queue, tree and graph operations, and the Big O complexity of each.
OCR A-Level Computer Science Active Recall Guide
Every question paired with its answer, grouped by topic and subtopic, ready to work in three passes.