Cambridge A Level Computer Science (9618): Hardware – Practice Questions

These are original questions written for Marlbridge, for revision and practice on this content. They are not reproduced past-paper questions, and they do not replicate the exam’s exact structure, question count or mark tariffs — Cambridge International holds copyright in its own papers. Use these alongside the official past papers available from your board.

Related: Hardware revision notes · Hardware study guide

These questions practise Topic 3 Hardware of Cambridge International AS & A Level Computer Science 9618, which is assessed in Paper 1 Theory Fundamentals. They cover every point in sections 3.1 (computers and their components) and 3.2 (logic gates and logic circuits). Answers are written in mark-scheme style: each [1] is one creditable point.

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Questions

1. Explain why a laptop computer needs both primary memory and secondary storage. [3]

2. A smart thermostat controls the heating in a house. It contains an embedded system.

(a) State what is meant by an embedded system. [1] (b) Give two benefits and one drawback of using an embedded system in the thermostat. [3]

3. Describe how a laser printer produces a printed page. [5]

4. Describe how data is read from an optical disc. [3]

5. A tablet computer has a capacitive touchscreen. Describe how the touchscreen detects where the user touches it. [3]

6. Explain how a buffer is used when a computer sends a long document to a printer. [3]

7. (a) Give two differences between SRAM and DRAM. [2] (b) State which of SRAM or DRAM is used for cache memory, and justify your choice. [2]

8. A games console stores its start-up program in ROM, and its manufacturer wants to send firmware updates to consoles already sold. Explain why EEPROM is more suitable than PROM or EPROM for this. [3]

9. A swimming pool’s water temperature is kept between 26 °C and 28 °C by a computer system.

(a) Explain why this is a control system and not a monitoring system. [2] (b) Describe how the system uses a sensor, an actuator and feedback to keep the water temperature in range. [4]

10. Draw up the truth table for the logic expression X = (A NOR B) OR (B AND C). Show a working column for each gate. [4]

11. A greenhouse sprinkler S switches on (S = 1) when:

• the soil is dry (D = 1) and it is daytime (T = 1), or
• the soil is dry and the manual override is off (M = 0).

(a) Write a logic expression for S. [2] (b) Complete the truth table for S. [4] (c) Describe the logic circuit for your expression, gate by gate. [2]

12. The truth table below shows the output Q of a circuit with inputs P and R.

P	R	Q
0	0	1
0	1	0
1	0	0
1	1	1

(a) Write a logic expression for Q. [2] (b) Name the single gate followed by a NOT gate that gives the same output. [1]

13. Explain how a microphone converts sound into data a computer can store. [3]

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Answers

1. Primary memory (RAM) holds the programs and data currently being used, because the processor can only execute instructions held in main memory [1]. RAM is volatile, so its contents are lost when the laptop is switched off [1]. Secondary storage is non-volatile and has a larger capacity, so it keeps the operating system, applications and files when the power is off [1].

2. (a) A computer system built into a larger device to perform a dedicated function [1]. (b) Benefits (any two): small enough to fit inside the thermostat [1]; cheap to mass-produce [1]; low power consumption [1]; reliable because it does only one task [1]. Drawback (any one): difficult for the owner to upgrade [1]; if connected to the internet it could be hacked [1]; faults need a specialist or replacement unit [1].

3. Any five, in a sensible order: the drum is given an electric charge [1]; a laser beam scans the drum and changes the charge on areas to form an image of the page [1]; the drum is coated with charged toner, which sticks only to the charged image [1]; paper is given a charge so it attracts the toner from the drum as it passes [1]; the fuser unit heats and presses the paper so the toner melts and fixes [1]; the charge is removed from the drum and excess toner is cleaned off ready for the next page [1].

4. A laser beam is shone onto the surface of the spinning disc [1]. The light is reflected differently by pits and lands (or by marked and unmarked areas) [1]. A photodiode / light sensor detects the reflected light, and the changes are converted into binary values [1].

5. The screen has a layer that holds an electrostatic field / charge [1]. Touching with a finger (a conductor) changes the capacitance at that point [1]. Sensors detect the change and the controller / processor calculates the coordinates of the touch [1].

6. The buffer is a temporary area of memory that holds the data waiting to be printed [1]. The processor fills the buffer quickly and can then carry on with other tasks [1]. The printer, which is much slower, takes data from the buffer at its own speed; when the buffer is empty it requests (e.g. by an interrupt) more data [1].

Tip: the buffer only stores data. Do not write that the buffer “sends” data; the processor or printer does the transfer.

7. (a) Any two: SRAM does not need refreshing, DRAM must be refreshed constantly [1]; SRAM is faster to access [1]; SRAM is more expensive per bit [1]; SRAM stores fewer bits per chip / is less dense [1]; SRAM uses flip-flops, DRAM uses capacitors [1]. (b) SRAM [1]. Cache must be as fast as possible to reduce the time the processor waits, and only a small amount is needed, so its higher cost is acceptable [1].

8. PROM can be programmed only once, so the firmware could never be updated [1]. EPROM must be removed from the console and erased with ultraviolet light, which owners cannot do [1]. EEPROM can be erased and rewritten electrically while it stays in the console, so an update can be installed in place [1].

9. (a) The computer does not just record or display the temperature [1]; it acts to change the temperature, by switching a heater on or off through an actuator [1]. (b) A temperature sensor measures the water temperature and sends readings (via an ADC) to the computer [1]. The computer compares each reading with the stored range 26–28 °C [1]. If the reading is below 26 °C, it sends a signal to an actuator to switch on the heater / open the hot-water valve; above 28 °C it switches it off [1]. Feedback: readings continue to be taken after the actuator acts, and each new reading determines the next action, so the temperature stays within range [1].

10.

A	B	C	A NOR B	B AND C	X
0	0	0	1	0	1
0	0	1	1	0	1
0	1	0	0	0	0
0	1	1	0	1	1
1	0	0	0	0	0
1	0	1	0	0	0
1	1	0	0	0	0
1	1	1	0	1	1

Marks: NOR column correct [1]; AND column correct [1]; X correct in rows 1–4 [1]; X correct in rows 5–8 [1].

11. (a) S = (D AND T) OR (D AND NOT M) [2]. One mark for each bracketed term joined correctly by OR. D AND (T OR NOT M) is also correct.

(b)

D	T	M	S
0	0	0	0
0	0	1	0
0	1	0	0
0	1	1	0
1	0	0	1
1	0	1	0
1	1	0	1
1	1	1	1

Marks: rows with D = 0 all 0 [1]; row 1,0,0 [1]; row 1,0,1 [1]; rows 1,1,0 and 1,1,1 [1].

(c) An AND gate with inputs D and T; a NOT gate on M feeding an AND gate with D [1]; the outputs of the two AND gates go into an OR gate whose output is S [1].

12. (a) Q = (NOT P AND NOT R) OR (P AND R) [2]. One mark per correct term. (b) XOR followed by NOT (an XNOR function) [1]. Q is 1 when the inputs are the same.

13. Sound waves make a diaphragm vibrate [1]. The vibration moves a coil in a magnetic field (or changes a capacitance), producing a varying analogue electrical signal [1]. An analogue-to-digital converter samples the signal and turns it into digital values that can be stored [1].

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Where marks are usually lost

• Repeating the example in the question (here, “it controls heating”) instead of giving a benefit for that device.
• Describing what a laser printer is used for instead of the stages of how it works.
• Saying that EPROM can only be written once; that describes PROM.
• Giving a monitoring answer (display, alarm) for a control question with no actuator.
• Missing rows in a truth table, or drawing NOR and XOR symbols that cannot be told apart.

Frequently asked questions

How are logic questions marked? Usually by groups of rows or by each correct gate, so a partly correct table still earns marks. Working columns help the examiner find your marks.

Can I give a simpler logic expression than the one the description suggests? Yes. Any expression that gives the same truth table is accepted, unless the question says which gates to use.

Which paper tests this topic? Paper 1 Theory Fundamentals (1 hour 30 minutes, 75 marks), which assesses sections 1 to 8 of the 9618 syllabus.

Official syllabus

Questions are written against Cambridge International AS & A Level Computer Science 9618, syllabus for 2026 and syllabus for 2027, 2028 and 2029, Topic 3 Hardware. For examiner comments by series, see the 9618 past papers page.