Edexcel GCSE Computer Science (1CP2) exam questions

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Practice paper

4 questions · 16 marks

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1Short recall2 marksStored Program Computers Swap Remove

Computers use the von Neumann stored program concept.

Define the term stored program concept.

[2 marks]

Mark scheme

Award one mark for any of the following up to a maximum of two marks:

Program instructions are stored in main memory/RAM (1)
The data used by the program is stored in main memory/RAM (1)
The CPU fetches/reads instructions from main memory to execute them (1)
The program can be run without the instructions being input again (1)

Allow 'the program is stored in memory' for one mark.

Do not accept answers about programs being stored on secondary storage, such as a hard disk or USB memory stick.

Do not accept answers that only describe the von Neumann architecture (e.g. having a CPU and memory) without stating that instructions are stored in main memory.

Example answers and how they were marked

Full marks2/2

Both the program instructions and the data the program uses are held in the same main memory, and the CPU fetches these instructions from memory to execute them.

Why: Instructions stored in main memory (1) and the CPU fetches instructions from memory to execute them (1).

Some marks1/2

Program instructions are stored in main memory.

Why: Instructions stored in main memory (1). No second point about data being stored in the same memory or about the CPU fetching instructions.

No marks0/2

The program is saved on the hard disk so that it can be loaded into RAM when the user runs it.

Why: A near-miss about secondary storage, which the mark scheme says not to accept; the stored program concept is about instructions being held in main memory.

2Short recall2 marksCompression Swap Remove

Files can be compressed before they are stored.

Define the term lossless compression.

[2 marks]

Mark scheme

Award one mark for any of the following up to a maximum of two marks:

Reduces/makes the size of a file smaller (1)
No data is lost/removed (during compression) (1)
The original file/data can be recreated/restored exactly (1)

Allow 'the compressed file takes up less storage space' for the first mark.

The second and third bullets are two ways of making the same point: award a maximum of one mark for them, so a response that says no data is lost and that the original file can be restored, but does not say the file is smaller, scores one mark.

Do not accept descriptions of lossy compression, e.g. 'it removes data that is not needed to make the file smaller'.

Ignore reference to download/transmission times, bandwidth and streaming, as these are benefits of compression and not part of the definition.

Example answers and how they were marked

Full marks2/2

Lossless compression reduces the size of a file without permanently removing any data, so the original file can be restored exactly.

Why: Reduces the size of a file (1) and no data is lost, so the original can be restored exactly (1); maximum of two marks reached.

Some marks1/2

It makes a file smaller so it downloads more quickly.

Why: Reduces the size of a file (1); the faster download is ignored as a benefit, not part of the definition.

No marks0/2

It removes data that is not needed to make the file smaller.

Why: Describes lossy compression, which the do-not-accept line rules out, so the mention of making the file smaller is not credited.

3Discuss6 marksUtility Software Swap Remove

A small graphic design company keeps all of its project files on one desktop computer. The computer's hard disk has failed and some files have been lost. The owner has been told to use backup software.

Discuss the backup strategy the company should use.

Your answer should include:

the types of backup that could be used
where and how often backups should be made
how the backups would be used if the hard disk failed again.

[6 marks]

Mark scheme

Indicative content

Types of backup that could be used

A full backup copies all of the company's project files every time it is run, so the whole set of files is held together in one backup.
A full backup takes longer to make and needs more storage space than an incremental backup.
An incremental backup copies only the files that have changed since the previous backup, so it is quicker to run each evening.
Restoring from incremental backups needs the last full backup plus every incremental backup made since, which takes longer and is more complex.
A weekly full backup with nightly incremental backups can be suitable for the company when the reason is explained using the properties of the two types.

Where and how often backups should be made

Backups should be kept on a separate device and, ideally, at a different location, so that a fire or theft in the office cannot destroy the computer and the backups together.
Backups should be made regularly, for example every evening, so that at most one day's design work would be lost.
Cloud storage can hold copies off-site automatically, without the owner taking a disk home.
An external hard disk or USB flash drive can be used as the backup medium, with a copy kept away from the office.

How the backups would be used if the hard disk failed again

If the hard disk fails again, the backup software is used to restore the latest full backup and any later incremental backups onto a replacement disk.
The restored project files allow the company to carry on working and meet its clients' deadlines.
The backups should be tested by restoring a file so that the company knows the backup is usable before it is needed.
Backup software does not repair the failed hard disk itself, so a replacement disk is still needed.

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 requires all three bullets to be developed and applied, including both types of backup (or a justified combination) and a restoration sequence; a response that describes only a full backup cannot reach Level 3.

An answer that explains only one type of backup with at most a brief location or frequency point and no developed restoration is Level 1 (1–2 marks). Credit one off-site point only: cloud storage, an external disk kept elsewhere and 'a different location' are the same point. Do not accept that backup software repairs a failed hard disk or recovers files that were never backed up; an answer that only makes this claim is Level 0. An unsupported weekly-full/nightly-incremental recommendation is not credited.

Example answers and how they were marked

Full marks6/6

The company should make a full backup once a week and incremental backups every evening. A full backup copies every project file, so the whole set is held in one place, but it takes a long time and a lot of space. An incremental backup copies only the files that have changed since the last backup, so it is quick enough to run each night. The backups should be copied to an external hard disk that the owner takes home, or uploaded to cloud storage, so that a fire or a theft cannot destroy the computer and the backups together. Backing up every evening means that at most one day's design work would be lost. If the hard disk fails again, the backup software is used to restore the latest full backup and then each incremental backup onto a new disk, so the company can carry on meeting its clients' deadlines.

Why: Level 3: full and incremental backups are explained and applied to a weekly and nightly schedule (AO1); off-site storage and the restore sequence onto a replacement disk are developed and clearly tied to the hard disk failure (AO2).

Some marks2/6

The company should back up its files to an external hard disk. A full backup copies all of the files, so the project files can be restored if the hard disk fails again. The backup should be kept in a different room in case there is a fire.

Why: Level 1: names a full backup and briefly links it to restoring files, and gives a weak location point, but there is no incremental backup, frequency or developed restore sequence, so the points remain basic and independent.

No marks0/6

Backup software repairs the hard disk when it fails, so the company will not lose anything and can open the files again.

Why: Level 0: the only claim is that backup software repairs the failed hard disk and prevents all loss, which the mark scheme does not accept; no valid type, location, frequency or restoration point is made.

4Discuss6 marksTranslators Swap Remove

A company writes a photo editing program in a high-level language. The company will sell the finished program to customers. Each customer will install the program on their own computer and run it many times.

Discuss whether the company should use a compiler or an interpreter to translate the program before it is sold.

Your answer should include:

the output of each type of translator
whether the program has to be translated each time it is run
what the customer needs on their computer to run the program.

[6 marks]

Mark scheme

Indicative content

The output of each type of translator

A compiler translates the whole program in one go and produces object code.
The object code is saved as an executable file, which is already in machine code so the processor can run it directly.
An interpreter does not produce object code, so no translated file exists for the company to save and sell.
An interpreter translates one line at a time and executes it immediately, but that translation is not kept.

Whether the program has to be translated each time it is run

Compiled code is translated once, so the executable can be run as many times as the customer likes without being translated again.
If the source code is edited, the whole program has to be compiled again to produce a new executable.
An interpreted program is translated again every time it is run, so a customer who runs the program often waits for translation at every run.
An executable runs faster than interpreted code because it is already in machine code.

What the customer needs on their computer to run the program

A customer who installs the executable needs no compiler on their computer, so the program will run straight away.
If the company supplied the source code instead, the customer would need an interpreter installed, and it would have to be an interpreter for their type of computer.
A customer given only the executable does not have the source code, so cannot change the program.

Conclusion

A compiler is the better choice for this company, because the executable can be sold and the customer runs it without it being translated again and without being given the source code.
Using an interpreter would mean supplying the source code to customers and translating the program on every run.

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 cover all three bullets for this company's program, including translating once rather than on every run, and reach a conclusion.

Do not accept 'a compiler fixes errors' (a compiler reports syntax errors at the end of translation, it does not fix them) or 'a compiler is easier to use' with no link to output, translation or the customer. Do not accept answers about translating to assembly language.

Example answers and how they were marked

Full marks6/6

The company should use a compiler. A compiler translates the whole program in one go and produces object code, which is saved as an executable file. This executable is already in machine code, so the customer's processor can run it directly. The program is translated only once, so a customer who runs the program many times does not wait for it to be translated again, and it runs faster than interpreted code would. An interpreter produces no object code, so the company would have nothing to sell as an executable. The customer would have to be given the source code and would need an interpreter installed on their computer, and the program would be translated again every time it was run.

Why: Level 3. Covers the output of both translators (executable from the compiler, no object code from the interpreter), the effect of translating once rather than on every run, and what the customer needs on their computer, all applied to the company selling the program, with a clear conclusion.

Some marks3/6

A compiler produces an executable file, which the company can save and sell to its customers. An interpreter does not produce an executable file, so the customer would need the source code and an interpreter installed on their computer to run the program. This means a compiler is better for the company, because customers can just run the file they are given.

Why: Level 2. Gives the output of both translators and links this to what the customer needs, with a conclusion, but never says the compiled program is translated once while an interpreted one is translated on every run, so the reasoning is not developed enough for Level 3.

No marks0/6

The company should use a compiler because it is easier to write programs with a compiler and it fixes the errors in the program before the customers get it.

Why: Level 0. No creditworthy point: 'easier to write programs' is not linked to the output, the translation each run or the customer, and 'fixes the errors' is a misconception, as the mark scheme's guidance says a compiler only reports errors at the end of translation.

Edexcel GCSE Computer Science (1CP2) Exam Questions

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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

4.2 Network security

5.1 Environmental

5.2 Ethical and legal

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