Edexcel GCSE Computer Science (1CP2) exam questions

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Practice paper

5 questions · 13 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.

2Short 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.

3Describe2 marksLow and High Level Languages Swap Remove

A device driver is software that allows the operating system to control a piece of hardware. Device drivers are often written in a low-level programming language.

Describe one reason why a low-level programming language is suitable for writing a device driver.

[2 marks]

Mark scheme

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

Instructions can manipulate/control the hardware/memory/registers directly (1) so the driver can control the specific device it is written for (1)
The code is written for one specific processor/architecture (1) so it works with the exact hardware it will control (1)
The programmer controls exactly how memory/registers are used (1) so the code is efficient and needs little memory, which suits a device that has limited memory (1)
Each instruction maps to one machine code instruction (1) so the driver code is small enough to fit in the memory of the device (1)

Extra detail, such as naming the device the driver controls, is not needed to earn the marks.

Do not accept 'it is closer to machine code' on its own: it must be developed to show how this helps the driver, e.g. it can control the hardware directly.

Do not accept 'it is faster/quicker' with no link to the hardware/device, e.g. the device responds quickly.

Do not accept 'it is easier to learn', 'it is easier to debug' or 'it takes less time to write'.

Example answers and how they were marked

Full marks2/2

Low-level instructions can manipulate the hardware and memory directly (1) so the driver can control the specific device it was written for, such as a sound card (1).

Why: Point about direct control of hardware/memory (1) linked to controlling the specific device (1). The named device is extra detail and is not needed.

Some marks1/2

Low-level instructions can manipulate the hardware directly.

Why: Correct point (1) but no linked development saying how this helps the device driver.

No marks0/2

It is closer to machine code so it runs faster than a high-level language.

Why: 'Closer to machine code' is not developed into how this helps the driver, and 'runs faster' is not linked to the hardware/device, so no mark.

4Calculate3 marksAdding Binary Numbers Swap Remove

Binary patterns can represent numbers.

(a)

Complete the table to show the 8-bit result of the binary addition.

[2 marks]

128	64	32	16	8	4	2	1
1	1	0	1	1	0	1	1
1	1	0	1	1	1	0	0

Mark scheme

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

1011 (1)
0111 (1)

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

Ignore a carry shown beyond the eighth bit.

Example answers and how they were marked

Full marks2/2

1011 0111

Why: 219 + 220 = 439, which needs 9 bits; the 8 bits that are kept are both correct (2).

Some marks1/2

0000 0111

Why: Forgets to carry the 1s. The second nibble is correct (1); the first is not.

No marks0/2

1101 1111

Why: Never carries. Neither nibble is correct.

(b)

State the name of the error that occurs when this addition is carried out.

[1 mark]

Mark scheme

Award one mark for:

overflow (error) (1)

Example answers and how they were marked

Full marks1/1

Overflow

Why: The result needs more bits than are available (1).

No marks0/1

Underflow

Why: A near miss: the result is too big for 8 bits, not too small.

No marks0/1

A syntax error

Why: A syntax error is a mistake in a program's code, not in arithmetic.

5Discuss6 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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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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