Edexcel GCSE Computer Science (1CP2) exam questions

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3 questions · 14 marks

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1Explain2 marksLow and High Level Languages Swap Remove

High-level languages are designed to be easier to learn than low-level languages.

Explain one reason why a high-level language is easier to learn than a low-level language.

[2 marks]

Mark scheme

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

Statements are written in English-like words/use maths symbols (1) so the programmer can understand more easily what each one does (1)
The language uses meaningful names for variables/structured constructs such as loops (1) so the code is easier to read/follow (1)
One statement translates into several machine code instructions (1) so there are fewer instructions to learn/understand for the same task (1)

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

Do not accept 'it is easier' / 'it is simpler' on its own, without saying what is easier/simpler.

Do not accept 'the computer understands it directly' / 'it does not need translating'.

Do not award answers about the program running faster or using less memory, as these are not about ease of learning.

Example answers and how they were marked

Full marks2/2

Statements are written in English-like words (1) so the programmer can understand more easily what each line does (1).

Why: Linked point (1) of English-like statements and reason (1) that these are easier to understand.

Some marks1/2

It uses meaningful names for variables (1) so it is easier.

Why: Point (1) that meaningful names for variables are used, but 'so it is easier' is not accepted as the linked reason.

No marks0/2

Because the computer can understand high-level code without translation.

Why: Misconception that high-level code is understood directly by the computer; no creditworthy characteristic of the language is given.

2Discuss6 marksLow and High Level Languages Swap Remove

A software company is writing a new program that will be sold to users who have different types of computer. The program does not need to control the hardware of the computer directly. The company must decide whether to write the program in a high-level language or a low-level language.

Discuss whether the company should use a high-level language or a low-level language to write this program.

Your answer should consider:

machine independence
processor specificity
how the code is translated for each type of computer.

[6 marks]

Mark scheme

Indicative content

Machine independence

A high-level language is machine independent, so the same source code can be run on different types of computer with few or no changes.
The company can write the program once and sell it to users with different computers, without rewriting the code for each type of computer.
Only one version of the program needs to be written and maintained, so development takes the company less time.

Processor specificity

A low-level language is processor-specific, so a program written for one processor will not run on a different processor without being rewritten.
Assembly language instructions depend on the instruction set of the particular processor, so the company would need a separate version of the program for each type of computer.
Writing a separate low-level version for every type of computer would take the company much longer than writing one high-level program.
Low-level code gives direct control of the hardware of one processor, so it is better suited to device drivers than to a program that must run on many different computers.

Translation

High-level source code is translated for each type of computer by a compiler or an interpreter, so one version of the source code is enough for all the users.
Assembly language is translated into machine code by an assembler, and the assembler produces machine code for one specific processor only.
Machine code is already in a form that one particular processor can execute directly, but the same machine code will not run on a different processor.
Each high-level statement translates into several machine code instructions, so the programmer does not need to know the instruction set of the 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)

Additional guidance

Level 3 responses must cover both high-level machine independence and low-level processor specificity, with the effect on the company's decision.
Do not award low-level language, assembly language or machine code as portable, or 'high-level languages are written in English/like English' as a reason for machine independence.

Example answers and how they were marked

Full marks6/6

A high-level language is machine independent, so the company can write the program once and it will run on different types of computer with few or no changes. A different compiler is used for each type of processor to translate that same source code into the machine code for that computer, so the company can sell one program to all of its users. A low-level language is processor-specific, so a program written in assembly for one processor will not run on a different one. The assembler produces machine code for one particular instruction set, so the company would need to write a separate version for each type of computer, which would take much longer. As the program does not need to control the hardware directly, the company should use a high-level language.

Why: Develops high-level machine independence with the compiler translating for each processor, and low-level processor specificity with the assembler producing machine code for one instruction set, both applied to the company's decision, in a coherent and sustained argument: Level 3, 6 marks.

Some marks3/6

A high-level language is machine independent, so the company can write the program once. A different compiler is used for each type of computer to translate the code, so users with different computers can all run the same program. A low-level language is processor-specific, so it would not be as suitable for the company.

Why: Machine independence is linked to the compiler and applied to the users, but processor specificity is only asserted and no translation of low-level code is given, so the reasoning is not sustained: Level 2, 3 marks.

Some marks1/6

High-level languages are machine independent because they are written in English, so the company can sell the program to anyone. Low-level languages are machine code, so they can be translated to run on any type of computer.

Why: One basic point that high-level languages are machine independent, applied by selling to anyone (1). 'Written in English' is not a reason for machine independence and low-level code is not portable, so neither is credited: Level 1, 1 mark.

3Discuss6 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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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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