Edexcel GCSE Computer Science (1CP2) Exam Questions

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

• Breaks messages/data into packets (1)
• Reassembles packets (at the destination) (1)
• Detects errors (1)
• Resends lost/missing packets/requests retransmission of lost packets (1)
• Creates/establishes a connection between two computers/hosts/sets up a connection before data is sent (1)

Do not accept routing packets or using IP addresses, which is the role of IP.

Do not accept encrypting data or providing security.

Do not accept vague answers such as 'transmits data' or 'sends data' without saying how TCP does this.

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

• Use of fossil fuels/non-renewable energy to power factories (1)
• Release of CO2/greenhouse gases (1)
• Mining/extraction of raw materials damages land/causes erosion (1)
• Use of large amounts of water (1)
• Pollution of water/land from waste produced during manufacturing (1)
• Transport of materials/parts causes emissions (1)

A single statement that names both a cause and its environmental effect can earn both marks, e.g. burning fossil fuels releases CO2.

Do not award both marks for two statements that describe the same issue in different words.

Do not accept disposal of devices at the end of their life/e-waste from discarded devices.

Do not accept 'energy consumption'/'uses electricity'/'uses energy' without a source or cause, such as fossil fuels or factories.

Do not accept vague references to 'rubbish'/'waste' without saying that it pollutes water/land.

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

• The same source code can be run on different types/makes of processor (1) with few or no changes being made to the program (1)
• A compiler/interpreter is available for each type of processor (1) to translate the source code into the machine code for that processor (1)
• The statements are not tied to one processor's instruction set (1) so the program is portable between different computers (1)

Do not accept 'it is translated by a compiler' on its own.

Do not accept 'the program does not need to be translated' or 'it is easier to use'.

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

• A licence/license is a legal agreement between the developer/owner and the user/end user/customer (1) that sets out what the user is/is not allowed to do with the software (1)
• It states how many devices/users may install or run the software (1) so the software is not installed/used on more devices/users than the developer allows (1)
• It protects the developer's intellectual property/copyright (1) by stopping the software being copied/used/redistributed without permission (1)
• It sets out the terms/conditions of use (1) that the user must agree to before using the software (1)

Allow a single unlinked point, such as 'it sets out what the user is allowed to do with the software', for one mark.

Do not accept 'it is a contract/a legal document' with no purpose given.

Do not accept descriptions of product keys, activation or how to install the software.

Do not accept answers that only describe copyright, patents or trademarks with no reference to a licence.

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

• More samples are taken every second / the sample rate is higher (1) so the digital wave follows the shape of the analogue wave more closely (1)
• The amplitude is measured more often / at shorter intervals (1) so fewer changes in the sound are missed between measurements (1)
• The sample interval is shorter (1) so less of the sound wave is lost/goes unrecorded between samples (1)
• More data points are recorded for the same length of sound (1) so the digital representation is a closer copy of the original sound (1)

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

Do not accept 'the quality is better/higher' or 'the sound is clearer' as a point on its own without a reason such as more samples or more detail.

Do not accept 'the samples are more accurate' or 'more data is collected' without saying what becomes more accurate or what the extra data records.

Do not accept 'the file size is larger' as a reason for improved quality.

Do not accept answers about using more bits per sample, as these describe bit depth, not the sample rate.

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

• Files can be organised into folders/directories (1) so users can find/store files easily (1)
• Files can be located/opened/saved (1) because the operating system keeps track of where each file is stored (1)
• Access permissions can be set on files (1) so only allowed users can read/modify them (1)
• Files can be copied/moved/deleted (1) because the operating system controls where data is written/removed on a storage device (1)
• Free disk space can be monitored/managed (1) so storage does not run out / files are stored efficiently (1)

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

Do not accept 'manages files' or 'organises files' on its own as it repeats the question.

Allow 'makes it easier to find files' as the linked reason for organising files into folders.

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

• If the data is intercepted, it cannot be read/understood (1) because it is scrambled and the attacker does not have the key (1)
• Only the intended receiver can decrypt the data (1) because they have the secret/shared decryption key (1)
• Data cannot be read if it is stolen/lost (1) because it can only be decrypted with the key (1)

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

A point on its own earns one mark; the second mark is only awarded for a reason linked to that point.

Do not accept 'because it is encrypted' as the reason, as this repeats the point.

Do not accept 'it stops the data being intercepted' because encryption does not prevent interception.

Do not accept 'it stops hackers' on its own without saying why the data cannot be read or used.

Do not accept vague answers such as 'it is more secure' or 'it keeps data safe' without saying how the data is protected, e.g. that it cannot be read without the key.

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

• (The attacker) watches/observes the user (1) as they type in their password/PIN (1)
• (The attacker) uses a camera/CCTV to record/film the user (1) as they type in their password/PIN (1)
• (The attacker) looks at the user's screen (1) and sees their password/account details (1)
• (The attacker) obtains the user's password/PIN by watching/observing them (1) so they can log in to the user's account (1)
• (The attacker) stands close to the user in a public place (1) so they can watch them type in their password/PIN (1)

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

The first mark is for the attacker watching/recording the user, or looking at their screen. The second mark is for naming what is obtained (a password/PIN or other information that is typed/displayed) or for how it is then used, e.g. to log in to the user's account.

Allow the first mark for watching/recording the user, or looking at their screen, even when the answer does not state what is typed or displayed.

Allow the second mark where the answer says what information is seen; the answer does not have to go on to describe the attack itself, e.g. logging in to an account.

Do not accept 'shoulder surfing' or 'looking over someone's shoulder' on its own, with no password/PIN or other information seen, as this repeats the question.

Do not accept 'the attacker steals/gets the password' without saying that it was obtained by watching/observing the user.

Do not accept other social engineering methods, such as phishing or baiting, that do not involve observing the user.

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

• 1010 (1)
• 0000 (1)

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

Indicative content

Why lossless compression is suitable

• No data is removed, so the original file can be restored exactly when it is decompressed.
• Source code must be reproduced exactly, because a single missing or changed character would stop the program working when it is run.
• A text document must keep every character, so that the meaning of the document is not changed.

How lossless compression makes a file smaller

• Run length encoding stores a repeated value once, together with a count of how many times it appears, so long runs of the same character are held in less space.
• Dictionary encoding finds patterns or words that are repeated in the text, stores each one once in a dictionary and replaces every occurrence with a short code.
• The more repetition there is in a file, the greater the reduction in size that can be achieved.

Benefits to the company

• The compressed files take up less space on the file server, so more programs and documents can be stored.
• There is less data to transfer, so backing the files up to another location finishes sooner.
• The company does not need to keep a separate uncompressed copy as well, because the compressed file can be restored exactly, which saves more storage space.
• The files must be decompressed before they are used, which takes time each time a file is opened.

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 why lossless compression is suitable and how it makes a file smaller.

Do not accept the idea that lossless compression removes data that is not needed.