Mark Scheme

Section A — Structured Questions

1. (a) (2) 0011 0101 = 32 + 16 + 4 + 1 = 53. 1 for correct place-value working, 1 for the answer 53. [2] (b) (4) 206 = 128 + 64 + 8 + 4 + 2 = 1100 1110. Marks for correct subtraction of place values and the correct 8-bit answer. (128+64=192, +8=200, +4=204, +2=206.) [4] (c) (up to 4) Binary is used because computers are made of switches/transistors that have only two states (on/off, 1/0), which binary represents reliably (2); a bit = a single binary digit (0 or 1); a byte = 8 bits (2). [4]

2. (a) (up to 2) The CPU (Central Processing Unit) is the part of the computer that processes instructions/data — it fetches, decodes and executes program instructions. [2] (b) (up to 4) Any two, 2 each: Control unit — directs the operation of the processor, controlling the fetch-decode-execute cycle; ALU — carries out arithmetic and logical operations; Registers — small, fast storage locations that hold data/instructions currently being processed. [4] (c) (up to 4) RAM is volatile (loses contents when power is off) and stores programs/data currently in use (2); ROM is non-volatile and stores permanent data such as the boot-up/BIOS instructions (2). [4]

3. (a) (up to 2) A protocol is a set of rules that governs how devices communicate/transmit data across a network. [2] (b) (up to 4) A LAN covers a small geographical area (e.g. one building/site) and is usually owned/managed by one organisation; a WAN covers a large geographical area (e.g. between cities/countries) and often uses third-party infrastructure (the internet is a WAN). Two clear differences. [4] (c) (up to 6) Encryption = scrambling data using a key so that it cannot be understood if intercepted; only someone with the correct key can decrypt/read it (up to 3, including why it matters — protects confidentiality of data such as passwords/payments). One other method (up to 3): firewalls, strong passwords/authentication, anti-malware, access rights. [6]

4. (a) (up to 2) An algorithm = a step-by-step set of instructions/rules for solving a problem or completing a task. [2] (b) (up to 4) The algorithm inputs five numbers, adds them to a running total, then divides the total by 5 to calculate and output the average (mean) of the five numbers (up to 3); the loop is a count-controlled (FOR) loop (1). [4] (c) (up to 6) A compiler translates the whole program into machine code before it runs, producing an executable; an interpreter translates and executes the code line by line as it runs (distinction up to 3). Advantage of compiler: runs faster once compiled / can distribute without source; advantage of interpreter: easier to test/debug (stops at the error line) / more portable (up to 3, one advantage each). [6]

Section B — Extended Response

5. (16 marks) Levels-marked discussion.

• Advantages of cloud storage: access from anywhere/any device with internet; automatic backups and off-site safety; scalable storage; less need to maintain local hardware; easy sharing/collaboration.
• Disadvantages: depends on a reliable internet connection; ongoing subscription cost; security/privacy concerns (data held by a third party); less control; potential for the provider's outage/breach.
• Considerations: internet reliability at the school; cost vs a local server; data protection of students' data; security measures (encryption, passwords); backup strategy; what happens if the provider fails.
• Level 4 (13–16): balanced discussion with developed advantages and disadvantages, relevant considerations and a justified conclusion; Level 3 (9–12): several developed points; Level 2 (5–8): limited/one-sided; Level 1 (1–4): basic.

Sample Answers with Examiner Commentary

Question 1(b) — Sample Answers

Grade A response. "To convert 206 into 8-bit binary I use the place values 128, 64, 32, 16, 8, 4, 2, 1. I check whether each fits into 206, largest first. 128 fits (1), leaving 206 − 128 = 78. 64 fits (1), leaving 78 − 64 = 14. 32 does not fit into 14 (0). 16 does not fit into 14 (0). 8 fits (1), leaving 14 − 8 = 6. 4 fits (1), leaving 6 − 4 = 2. 2 fits (1), leaving 2 − 2 = 0. 1 does not fit (0). Reading the digits gives 1100 1110."

Mark: 4/4. Examiner commentary: A complete, correct conversion that shows every step of the working, which the question explicitly requires. The candidate uses the standard place-value subtraction method, records a 1 or 0 for each place value, and arrives at the correct 8-bit answer 1100 1110. Showing the running subtraction (206 → 78 → 14 → 6 → 2 → 0) means that even a small slip would still earn method marks; here the method and answer are both correct.

Grade C response. "206 = 11001110"

Mark: 2/4. Examiner commentary: The final binary answer is correct, which earns the answer marks. However, the question says 'show your working', and this response shows none. In a four-mark conversion question, roughly half the marks are for the method — the place values used and the subtraction at each step. Had the answer been wrong, no method marks could have been awarded either. The candidate should always set out the place-value subtraction to secure the full four marks and protect against arithmetic slips.

Question 4(c) — Sample Answers

Grade A response (extract). "A compiler and an interpreter are both translators that turn high-level source code into machine code the computer can run, but they work differently. A compiler translates the entire program in one go, before it is run, and produces a separate executable file; the program then runs directly. An interpreter, by contrast, translates and executes the program one line at a time while it is running, without producing a separate executable. One advantage of a compiler is that the compiled program runs faster, because it has already been fully translated and does not need translating again each time it runs. One advantage of an interpreter is that it is easier to test and debug, because it stops at the exact line where an error occurs, making mistakes easier to find during development."

Mark: 6/6. Examiner commentary: A full-mark answer. The candidate draws a clear distinction — whole program before running (compiler) versus line by line during running (interpreter) — and correctly notes the compiler produces an executable. Crucially, they then give one valid, well-explained advantage of each (compiler: faster execution because already translated; interpreter: easier debugging because it stops at the error line). Explaining why each advantage holds, not just stating it, is what secures all six marks.

Grade C response. "A compiler translates all the code at once and an interpreter does it line by line. A compiler is faster and an interpreter is easier to fix errors with."

Mark: 4/6. Examiner commentary: The candidate correctly distinguishes the two translators (whole program versus line by line) and names a valid advantage of each, earning four marks. To reach full marks, the two advantages need brief development: why a compiled program is faster (it is already fully translated, so no translation is needed at run time) and why an interpreter makes debugging easier (it halts at the line where the error occurs). Adding that reasoning would gain the final two marks.