Edexcel GCSE Computer Science (1CP2) exam questions

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5 questions · 16 marks

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1Multiple choice1 markStored Program Computers Swap Remove

Identify the function of the control unit in the fetch-decode-execute cycle.

[1 mark]

ADecodes instructions
BPerforms arithmetic operations
CStores data and instructions
DTemporarily stores data being processed

Mark scheme

A Decodes instructions (1)
The only correct answer is A. The correct answer is Decodes instructions.
B is not correct because the arithmetic logic unit performs arithmetic operations
C is not correct because main memory stores data and instructions
D is not correct because registers temporarily store data being processed

Example answers and how they were marked

Full marks1/1

A Decodes instructions

Why: Correct option: the control unit decodes instructions during the fetch-decode-execute cycle (1).

No marks0/1

C Stores data and instructions

Why: Main memory stores data and instructions, not the control unit; this is a common distractor, so no mark.

No marks0/1

B Performs arithmetic operations

Why: Arithmetic operations are performed by the ALU, not the control unit; a common confusion between CPU components, so no mark.

2Multiple choice1 markCharacter Sets Swap Remove

A text file stores each character using 7-bit ASCII.

Identify the denary ASCII code for the space character.

[1 mark]

Mark scheme

A 32 (1)
The only correct answer is A. The correct answer is 32.
B is not correct because 33 is the ASCII code for the exclamation mark (!)
C is not correct because 48 is the ASCII code for the character 0
D is not correct because 65 is the ASCII code for the uppercase letter A

Example answers and how they were marked

Full marks1/1

A 32

Why: Correct option: the space character has the ASCII code 32 (1).

No marks0/1

C 48

Why: Near miss scoring 0: 48 is the ASCII code for the character 0, not the space character.

No marks0/1

D 65

Why: Misconception scoring 0: 65 is the ASCII code for the uppercase letter A, so a well-known code is given but not the code for a space.

3Describe2 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.

4Discuss6 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.

5Discuss6 marksTranslators Swap Remove

A student is writing a program in a high-level language. The student runs the program after every small change to check that it works.

Discuss whether the student should use an interpreter or a compiler while writing and testing the program.

Your answer should include:

how each translator deals with a syntax error
how much of the program is translated at a time
how this affects the student's testing.

[6 marks]

Mark scheme

Indicative content

How each translator deals with a syntax error

An interpreter stops as soon as it finds a syntax error and displays an error message.
With an interpreter, the lines before the error have already been executed, so the student can see how far the program got before it stopped.
A compiler reports errors at the end of translation, so the student gets a list of all the syntax errors in the program in one go.

How much of the program is translated at a time

An interpreter translates one line at a time and executes each line immediately.
A compiler translates the whole program in one go before any of it is run.
A compiler produces object code, so after every change the whole program must be compiled again before the student can run it.
An interpreter produces no object code, so the student does not have to wait for the whole program to be translated before it runs.

How this affects the student's testing

An interpreter suits this student because the program can be run straight away after each small change.
The interpreter stops at the first error found, so the student fixes that error and runs the program again, but may only find the next error on the next run.
Reporting every error at the end of compilation means the student can fix several errors at once, but cannot run the program until the whole program compiles.
The student should use an interpreter while testing, and compile the finished program once it works.

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)

Level 3 responses must relate the way each translator works to the student's testing, not just describe the two translators.

Do not accept answers about run-time or logic errors where no comparison of the translators is made.

Example answers and how they were marked

Full marks6/6

The student should use an interpreter while testing. An interpreter translates one line at a time and executes each line straight away, so as soon as the student has made a small change the program can be run without waiting for the whole program to be translated. If there is a syntax error, the interpreter stops at that line and displays an error message, and the lines before it have already been executed, so the student knows exactly where the problem is. A compiler translates the whole program in one go and only reports the errors at the end, so the student would get a list of all the syntax errors, but could not run any of the program until the whole program compiled successfully.

Why: Explains how each translator deals with a syntax error, how much is translated at a time (one line executed immediately against the whole program at once) and links both to the student's testing, with a conclusion. Level 3.

Some marks4/6

An interpreter translates one line at a time and stops when it finds an error, so the student can see where the error is. A compiler translates the whole program and reports all the errors at the end. The interpreter is better for testing because the student can run the program straight away after a change.

Why: Adequate: correct points about error reporting and one line at a time, with a recommendation, but the effect on testing is only asserted rather than reasoned through, so the linkage is not sustained. Level 2.

Some marks1/6

The student should use a compiler because it translates the program one line at a time and stops at the first error, which makes testing quicker.

Why: The roles of the two translators are reversed, so the answer only makes a basic point about testing more quickly. Level 1.

Edexcel GCSE Computer Science (1CP2) Exam Questions

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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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