Edexcel GCSE Computer Science (1CP2) Exam Questions

• B 4 (1)
• The only correct answer is B. The correct answer is 4 (2 bits give 2^2 = 4 values).
• A is not correct because 2 is the number of bits used to store each sample
• C is not correct because 8 different amplitude values would need 3 bits
• D is not correct because 16 different amplitude values would need 4 bits

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

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

• A binary digit (1)
• Has the value 0 or 1 (1)
• The smallest unit of data storage (1)
• A single 0 or 1 (1)

Allow binary digit/binary place value for binary digit

Allow a single binary digit for a single 0 or 1

Do not accept a group of 8 bits/half a nibble of 4 bits, which describe a byte or a nibble

Do not accept a binary number/binary on its own

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

• The processor/CPU can only execute machine code/binary instructions (1) so the assembly instructions must be converted into machine code before the program can run (1)
• Each assembly instruction/mnemonic matches/corresponds to one machine code instruction (1) so each line must be replaced with the machine code the processor executes (1)
• The program is written using mnemonics (1) that must be translated into machine code for the processor to carry out the instructions (1)
• The hardware/processor does not understand assembly language directly (1) so it must be translated into machine code that the processor can execute (1)

Do not accept 'assembly language is a low-level language'.

Do not accept 'it is hard to understand' or 'it is not English'.

Do not accept benefits, such as 'machine code runs faster' or 'the program will run more quickly'.

Do not accept 'an assembler/a translator converts it' on its own, with no reference to the processor only being able to execute machine code/binary.

Do not accept responses about high-level languages or about compilers/interpreters.

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.

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.