Edexcel GCSE Computer Science (1CP2) exam questions

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Practice paper

4 questions · 15 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.

2Explain2 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.

3Discuss6 marksUser Management Swap Remove

A school library has 24 computers that are shared by students and teachers throughout the day. Each computer runs an operating system. The school wants users' work to be kept private and the computers to be used only by authorised people.

Discuss how the operating system's user management features can be used to share the computers securely.

Your answer should include:

user accounts
authentication
the benefits for the school.

[6 marks]

Mark scheme

Indicative content

User accounts

Each student and teacher should have their own user account, so the operating system can identify the person who is logged on.
The operating system keeps a record of all valid users on the computer, so unknown users are not allowed to log in.
A separate home area or folder can be created for each account, so a student's saved work is kept apart from other users' work.
An account can be disabled when a student leaves the school, so they can no longer access the computers.

Authentication

A username and password can be required at login, so only users with the correct details can use the computer.
The operating system checks the entered password against the stored password for that account before allowing access.
Users should be encouraged to choose a strong password, which makes it harder for someone else to guess and log in.
The operating system can lock an account after several failed login attempts, which reduces the chance of someone trying passwords repeatedly.

Benefits for the school

Many students can share the same computers because each person's files are kept separate.
Work is less likely to be deleted or changed by another student, because users only see their own files.
The school can see which account was used on a computer, so misuse can be traced to a user.
Teachers can be confident that only authorised people can use the library computers.
The school does not need a separate computer for every student, so it saves money.

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 both user accounts and authentication, and apply them to the school library.

Do not accept general operating system functions such as file management or process management unless they are explicitly linked to managing users.

Example answers and how they were marked

Full marks6/6

Each student and teacher should have their own user account with a username and password. When someone logs in, the operating system checks the password against the one stored for that account, so only authorised people can use the computer. Each account can have its own home folder, so a student's work is kept private and another student cannot open or delete it. If a student leaves the school, their account can be disabled so they cannot log in again. This lets the school share a smaller number of computers safely, as each user's work stays separate and any misuse can be traced to the logged-in account.

Why: Level 3. It explains user accounts, authentication and benefits, with sustained links to sharing computers in the school library.

Some marks4/6

Every user should have a username and password. The operating system checks the password so that people who are not allowed cannot log in. Each user should also have their own area to save files so they do not delete other people's work.

Why: Level 2. Basic accounts and authentication points are made and linked, but the benefits to the school are only briefly applied and not developed.

No marks0/6

The operating system manages the users by looking after the files in folders and by making sure the printer works for everyone. It also keeps the computer running quickly when lots of students use it.

Why: Level 0. These are general operating system functions such as file management and peripheral management, not user management, so no creditworthy point is made.

4Discuss6 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

4.2 Network security

5.1 Environmental

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