Edexcel GCSE Computer Science (1CP2) exam questions

Build a practice paper from 514 exam-style questions, each with its mark scheme and example answers. Print it, or answer it on paper and then open the mark schemes. Or browse the questions by topic.

Practice paper

9 questions · 23 marks

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1Multiple choice1 markStored Program Computers Swap Remove

Identify the bus that carries addresses in one direction only, from the CPU to main memory.

[1 mark]

AAddress bus
BControl bus
CData bus
DSystem bus

Mark scheme

A Address bus (1)
The only correct answer is A. The correct answer is address bus. Do not accept 'address' on its own.
B is not correct because the control bus carries control signals in both directions between the CPU and other components
C is not correct because the data bus carries data in both directions between the CPU and main memory
D is not correct because the system bus is the collection of all three buses

Example answers and how they were marked

Full marks1/1

A Address bus

Why: Correct option: the address bus carries addresses in one direction only, from the CPU to main memory (1).

No marks0/1

C Data bus

Why: The data bus carries data in both directions, so it is not the bus that carries addresses in one direction only from the CPU to main memory; no creditworthy point.

No marks0/1

B Control bus

Why: The control bus carries control signals in both directions, not addresses in one direction only; this is the common control/address bus confusion, so no mark.

2Multiple choice1 markSound Swap Remove

A sound wave is sampled and the amplitude of each sample is stored using 2 bits.

Identify the number of different amplitude values that can be stored for each sample.

[1 mark]

Mark scheme

B 4 (1)
The only correct answer is B. The correct answer is 4 (2 bits give 2^2 = 4 values).
A is not correct because 2 is the number of bits used to store each sample
C is not correct because 8 different amplitude values would need 3 bits
D is not correct because 16 different amplitude values would need 4 bits

Example answers and how they were marked

Full marks1/1

B 4

Why: Selects the only correct option (1).

No marks0/1

C 8

Why: Near miss: 8 values would need 3 bits, one more than this recording uses (0).

No marks0/1

A 2

Why: Typical misconception: 2 is the number of bits, not the number of amplitude values those bits can store (0).

3Short recall1 markSecondary Memory Swap Remove

Data is stored on optical discs as pits and lands.

Name the component in an optical disc drive that reads this data.

[1 mark]

Mark scheme

Award one mark for:

Laser (1)

Allow laser beam

Do not accept read/write head

Do not accept pits

Do not accept lands

Do not accept reflective surface

Do not accept magnet/magnetic

Example answers and how they were marked

Full marks1/1

Laser

Why: Laser is the creditworthy answer (1).

No marks0/1

A read/write head

Why: Read/write head is not accepted by the mark scheme; it reads magnetic media, not optical discs, so no marks are awarded.

No marks0/1

Pits and lands

Why: Pits and lands are what the laser reads, not the component that reads the data, so the mark scheme does not accept them.

4Describe2 marksUtility Software Swap Remove

A hard disk can become fragmented as files are saved and deleted.

Describe how disk defragmentation software improves the performance of a hard disk.

[2 marks]

Mark scheme

Award up to two marks for a linked description such as:

Parts of a file are moved so they are stored together/in consecutive locations (1) so the read/write head has less distance to travel to read the file (1)
Files are rearranged so that each file is stored in one block (1) which reduces the time taken to open/load the file (1)
Free space on the disk is collected into one area (1) so new files can be saved without becoming fragmented (1)
The parts of each fragmented file are put in order (1) so fewer movements of the read/write head are needed to read it (1)

Do not accept responses about compressing files, deleting files or increasing the amount of storage, as these are not what defragmentation software does.

Do not accept 'it makes the disk faster' without saying how the files are changed.

Example answers and how they were marked

Full marks2/2

It moves the parts of a file so they are stored together in consecutive locations (1), so the read/write head does not have to move as far and the file opens more quickly (1).

Why: Linked point (1) and development (1): the file parts are stored together, which reduces read/write head movement.

Some marks1/2

It reorganises the files on the hard disk so that they are stored together.

Why: The point is made (1) but there is no development saying how this improves performance, so the second mark is not awarded.

No marks0/2

It compresses the files so that they take up less space on the disk.

Why: This describes data compression software, which the mark scheme says is not accepted; no creditworthy point is made.

5Describe2 marksTranslators Swap Remove

High-level code can be translated by a compiler or by an interpreter.

Describe how a compiler translates high-level code differently from an interpreter.

[2 marks]

Mark scheme

Award up to two marks for a linked description such as:

The compiler translates the whole program/complete source code in one go (1) whereas the interpreter translates one line/statement at a time (1)
The compiler translates all of the source code before any of it is run/executed (1) but the interpreter translates each line/statement as it reads it (1)
The interpreter translates one line/statement at a time (1) and the compiler translates the whole program/source code together (1)

Accept the compiler point and the interpreter point in either order.

Do not accept responses about object code/executable files, when the translated code is executed, how errors are reported, or speed/memory use.

Do not accept 'the interpreter executes/runs each line' on its own, without saying that it translates one line/statement at a time.

Example answers and how they were marked

Full marks2/2

A compiler translates the whole program in one go, while an interpreter translates one line at a time.

Why: Whole program translated in one go (1) and interpreter translates one line at a time (1).

Some marks1/2

A compiler translates the whole program in one go.

Why: Whole program translated in one go (1); no linked point about the interpreter translating a line at a time.

No marks0/2

A compiler produces an executable file, but an interpreter does not.

Why: Describes the output, not the amount translated at a time; object code/executable files are not accepted.

6Explain2 marksProtocols & Layers Swap Remove

Two computers exchange data over a network.

Explain why network protocols are needed for the two computers to communicate.

[2 marks]

Mark scheme

Award up to two marks for a linked explanation such as:

Devices (can) understand/interpret the data they receive (1) because they follow the same set of rules for communication (1)
Data is sent in an agreed format/structure (1) so the receiving device can interpret/understand it correctly (1)
Devices (can) connect/communicate successfully (1) because they agree how the data is transmitted, such as the type of signal used (1)
Errors (can) be detected/handled (1) because both devices follow the same rules for checking the data (1)

For both marks, the expansion must follow/associate with the statement.

Do not accept 'so devices can talk/communicate with each other' or 'so they can understand each other' without saying they follow the same rules/agreed format.

Do not accept an answer that only states protocols are a set of rules, without saying what this allows (e.g. the data can be understood/interpreted).

Do not accept a faster connection/speed as a reason why protocols are needed.

Do not accept naming a protocol (e.g. TCP/IP, HTTP, Wi-Fi) without an explanation of why it is needed.

Do not accept a description of what a protocol does (e.g. 'TCP splits data into packets') without saying why this is needed.

Example answers and how they were marked

Full marks2/2

Devices can understand the data they receive (1) because they follow the same set of rules for communication (1).

Why: Linked point (1) and reason (1): following the same rules is what lets the devices understand the data.

Some marks1/2

Data is sent in an agreed format (1).

Why: Point (1) identified, but no linked reason saying what the agreed format achieves.

No marks0/2

Protocols are needed so the connection is faster (0) because more data can be sent at once.

Why: Speed is not a reason protocols are needed, so there is no creditworthy point or linked reason.

7Calculate2 marksBinary Shifts Swap Remove

Computers manipulate binary patterns.

Complete the table with the result of applying the shift to the binary pattern.

[2 marks]

Binary pattern	Shift	8-bit binary result
1000 0001	Logical shift right by 1

Mark scheme

Award one mark for each correct nibble in the correct order:

0100 (1)
0000 (1)

0 marks if the response is not 8-bit binary.

Example answers and how they were marked

Full marks2/2

0100 0000

Why: Every bit moves 1 place right, with 0s in from the left: both nibbles are correct (2).

Some marks1/2

0100 0001

Why: A slip in the last bit. The first nibble is correct (1); the second is not.

No marks0/2

0000 0010

Why: Shifts the bits the wrong way. Neither nibble is correct.

8Discuss6 marksPurpose & Function of Operating Systems Swap Remove

A home computer is used to stream music, edit a video and download files at the same time.

Discuss how the operating system manages the processes running on the computer.

Your answer should include:

how the CPU is shared between processes
the states a process can be in
how the operating system responds when a process needs attention

[6 marks]

Mark scheme

Indicative content

How the CPU is shared between processes

The operating system uses multitasking to give each process a short time slice on the CPU, so the music, video editor and download appear to run at the same time.
The operating system decides which ready process will run next, so one program cannot keep the CPU to itself.
The operating system can stop a running process and move it back to ready when its time slice ends, so all processes make progress.

The states a process can be in

When a program is opened, the operating system creates a process and moves its instructions into RAM so it is ready.
The operating system moves a ready process to running when the CPU is free.
A running process becomes blocked when it is waiting for input or data, such as the download waiting for data to arrive.
When the process finishes, the operating system terminates it and releases the resources it was using.

How the operating system responds when a process needs attention

An interrupt is a signal to the CPU that needs immediate attention, so the operating system suspends the current process and runs the interrupt handler.
A hardware interrupt could be a printer out of paper, and a software interrupt could be an error in a program.
After the interrupt has been handled, the operating system can return the interrupted process to the CPU.

Levels

Level 0 (0 marks): No rewardable content.
Level 1 (1–2 marks): Basic, independent points are made, showing elements of understanding of key concepts/principles of computer science. (AO1) The discussion will contain basic information with little linkage between points made or application to the context. (AO2)
Level 2 (3–4 marks): Demonstrates adequate understanding of key concepts/principles of computer science. (AO1) The discussion shows some linkages and lines of reasoning with some structure and application to the context. (AO2)
Level 3 (5–6 marks): Demonstrates comprehensive understanding of key concepts/principles of computer science to support the discussion being presented. (AO1) The discussion is well developed, with sustained lines of reasoning that are coherent and logically structured, and which clearly apply to the context. (AO2)

Additional guidance

Level 3 responses must cover at least two of scheduling, process states and interrupts.
A response that only states that the OS 'manages processes' or gives a program a turn, without expansion, is limited to Level 1.

Example answers and how they were marked

Full marks6/6

The OS uses multitasking to share the CPU. It gives each process, such as the music player and the video editor, a small time slice so they appear to run at the same time. It decides which ready process is next and how long it runs. When the video editor is opened, the OS creates a process and moves its instructions into RAM so it is ready; when the CPU is free it moves it to running. If the download is waiting for data, the OS marks it blocked so the CPU is not wasted. If the printer runs out of paper, a hardware interrupt tells the CPU to stop and run the interrupt handler; afterwards the OS returns to the process.

Why: Covers scheduling with time slices, process states (ready, running, blocked) and interrupts, with sustained application to the music, video editor and download. Level 3.

Some marks4/6

The operating system uses multitasking so the music and video editor can run at the same time. It gives each program a small amount of time on the CPU. When a program is opened it creates a process and puts it in RAM. If a process is waiting for input it is blocked.

Why: Covers CPU sharing and process states, with some application, but says nothing about interrupts. Level 2.

Some marks1/6

The operating system manages processes by giving each program a turn on the CPU. This stops the computer crashing when too many programs are open.

Why: Gives only a basic, undeveloped point about giving each program a turn, with no linkage or application. Level 1.

9Discuss6 marksLow and High Level Languages Swap Remove

A company is developing the firmware for a robotic vacuum cleaner. The firmware must read the distance sensors and control the motors. The vacuum cleaner has a small amount of memory.

Discuss the characteristics of a low-level programming language that make it suitable for writing the firmware.

Your answer should include:

control of the hardware
the efficiency of the code
the link between the language and the processor.

[6 marks]

Mark scheme

Indicative content

Control of the hardware

Low-level languages can read and write the contents of registers and memory addresses directly, so the firmware can take the values from the distance sensors without calling a library routine.
Assembly language instructions can read from and write to specific input/output ports on the vacuum cleaner's processor, so the motors can be switched on and off directly.
The programmer decides exactly which processor operations are carried out and in which order, which matters when the vacuum must reverse away from a step or an obstacle.
A low-level language puts nothing between the program and the hardware, so the programmer can control the hardware of the vacuum cleaner precisely.

Efficiency of the code

Assembly language code can be hand-optimised instruction by instruction, so the code that checks a sensor is as short as possible.
The programmer can choose which registers hold values that are used again and again, which cuts down the number of memory accesses the firmware needs.
A hand-written low-level program can be made compact, so it is more likely to fit in the small amount of memory the vacuum cleaner has.
Because each instruction does one defined job, the time taken to react to a sensor reading is predictable, which suits firmware that must not overrun.

Link between the language and the processor

Low-level languages are processor-specific, so the instructions used are those of the exact processor in the vacuum cleaner rather than general statements that need translating.
Each assembly language instruction maps to one machine code instruction, so the programmer knows precisely which processor operation will be carried out by each line of code.
An assembler turns each mnemonic into its machine code equivalent, so the machine code running on the vacuum cleaner's processor is exactly what the programmer wrote.
Code written for a different processor would have to be rewritten, which is acceptable here because the vacuum cleaner always uses the same processor.

Levels

Level 0 (0 marks): No rewardable content.
Level 1 (1–2 marks): Basic, independent points are made, showing elements of understanding of key concepts/principles of computer science. (AO1) The discussion will contain basic information with little linkage between points made or application to the context. (AO2)
Level 2 (3–4 marks): Demonstrates adequate understanding of key concepts/principles of computer science. (AO1) The discussion shows some linkages and lines of reasoning with some structure and application to the context. (AO2)
Level 3 (5–6 marks): Demonstrates comprehensive understanding of key concepts/principles of computer science to support the discussion being presented. (AO1) The discussion is well developed, with sustained lines of reasoning that are coherent and logically structured, and which clearly apply to the context. (AO2)

Within Level 1, award 1 mark for a single basic point and 2 marks for two or more independent basic points; Level 2 requires the points to be linked to the vacuum cleaner; Level 3 requires both control of the hardware and efficiency of the code, and a few concise, linked sentences can reach Level 3, so extra length is not required.

Accept registers, memory addresses, input/output ports, machine code and mnemonics as ways of describing access to the hardware, and accept 'a low-level language is faster' as a basic point on its own. Do not award 'binary is a low-level language' (machine code is written in binary, but binary is not a language), or characteristics of high-level languages such as being easy to read or portable, as characteristics of a low-level language.

Example answers and how they were marked

Full marks6/6

A low-level language can read and write to registers and to input/output ports directly, so the firmware can take the distance sensor readings and switch the motors without needing library routines. It can be hand-optimised instruction by instruction, so the code that checks a sensor is short and the time it takes is predictable, and a compact program is more likely to fit in the vacuum cleaner's small memory. The language is processor-specific and each assembly instruction maps to one machine code instruction, so the programmer knows exactly which operation the vacuum's processor will carry out, and the assembled machine code is exactly what they wrote.

Why: Covers all three bullets: direct control of registers and ports applied to the sensors and motors, hand-optimised compact code with predictable timing applied to the small memory, and the one-to-one link to the processor's own instruction set. Linked and applied throughout, so Level 3.

Some marks2/6

A low-level language can control the hardware directly. It can read the sensors and control the motors. It is also faster than a high-level language, so the vacuum responds quickly. This is useful because it has little memory.

Why: Three basic, independent points: direct control of the hardware applied to the sensors and motors, faster execution, and suitability for limited memory. They are asserted without development (no registers, ports or predictable timing) and the link between the language and the processor is missing, so Level 1, two or more basic points (2).

Some marks1/6

A low-level language is written in binary, so the computer can understand it directly. It is faster than a high-level language.

Why: 'Faster than a high-level language' is a creditworthy basic point (1). 'Written in binary' is not awarded, as binary itself is not a language and the do-not-award rule applies. Only one undeveloped point with no application to the vacuum cleaner, so Level 1, single basic point (1).

Edexcel GCSE Computer Science (1CP2) Exam Questions

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Practice paper

Questions by topic

2.1 Binary

2.2 Data representation

2.3 Data storage and compression

3.1 Hardware

3.2 Software

3.3 Programming languages

4.1 Networks

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