About Processor, hardware and system software in A Level Computer Science
Processor, hardware and system software is one of the 10 main topics in our A Level Computer Science (Cambridge (CAIE) 9618) question bank, and about 13% of its real questions come from it. Tayyari Karo has 147 real questions on this topic from 2021 to 2026, from Paper 1, Paper 3. By difficulty: 75 medium, 58 easy, 14 hard.
Work through the questions below, then open the explanation for each one. Redo the ones you missed a few days later.
Try 8 real questions
These are real past-paper questions. Think of your answer first, then open the explanation.
May/June 2026 · Paper 1 · Processor, hardware and system software
A computer programmer uses language translators; two types are an interpreter and a compiler. (a) Explain why language translators are needed when programming. [2]
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1 mark each to max 2: to convert a high-level language to a low-level language/assembly/machine code; computers use machine code and programmers use high-level languages; to allow the computer to process the coded statements.
Computers run only machine code, so code written in a high-level language must be translated.
May/June 2025 · Paper 3 · Processor, hardware and system software
(a) Describe what is meant by multi-tasking and how it benefits process management.
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• Running multiple processes concurrently
• Which benefits process management by allowing more tasks to complete than would be the case if they had to run one task after another
2 marks: 1 for each.
October/November 2025 · Paper 3 · Processor, hardware and system software
Write the Reverse Polish Notation (RPN) for: (2 – 6) * (13 + 7) / 5
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2 6 – 13 7 + * 5 /
Two marks for correct RPN.
October/November 2024 · Paper 1 · Processor, hardware and system software
(d)(i) Describe the principal operation of an optical disc reader/writer.
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• The disc is spun at high speed
• A laser is shone onto the disc to read/write using optical head to move it into position
• It follows the spiral track from the centre outwards
• When writing the laser burns pits to represent the data
• When reading the laser reflects from pits and lands
• The reflection from a pit and a land is different
• The differences are interpreted as 1 or 0
4 marks: 1 for each bullet point to max 4.
May/June 2023 · Paper 1 · Processor, hardware and system software
6 An interrupt is generated when a key is pressed on a computer keyboard. Explain how the computer handles this interrupt.
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• An interrupt flag is raised in the (interrupt) register
• At the end of the current FE cycle / at the start of the next FE cycle
• The system checks the interrupt register for higher priority interrupts than current process
• If true, it stores the current contents of the registers on the stack
• The appropriate interrupt service routine (ISR) for the key press is called
• The input data from the keyboard is processed
• The contents of the registers are restored from the stack and control is passed back to previous process
5 marks: 1 each to max 5.
October/November 2023 · Paper 1 · Processor, hardware and system software
(c)(ii) The current contents of the ACC are: 00010111
Show the contents of the ACC after: LSR #3
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00000010
1 mark.
October/November 2022 · Paper 1 · Processor, hardware and system software
(b)(ii) The current contents of the ACC are: 10010011
Show the result after the execution of: AND B11110000
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10010000
1 mark.
May/June 2022 · Paper 1 · Processor, hardware and system software
A computer system is designed using the basic Von Neumann model.
(a)(i) Describe the role of the registers in the Fetch-Execute (F-E) cycle.
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Any five of:
- The Program Counter (PC) holds the address of the next instruction...
- ...and its contents are incremented / changed to the next address each cycle.
- The Memory Address Register (MAR) holds the address to fetch the data (from the PC).
- The Memory Data Register (MDR) holds the data at the address in MAR.
- The instruction is transferred to the Current Instruction Register (CIR) for decoding and execution.
5 marks: 1 per point to max 5.
