Oxford Cambridge and RSA

GCSE (9–1) Computer Science

J277/01: Computer Systems


General Certificate of Secondary Education

Mark Scheme for June 2026

MARKING INSTRUCTIONS

PREPARATION FOR MARKING

  1. Make sure that you have read and understood the mark scheme and the question paper for this unit.
  2. Log-in to RM Assessor and mark the required number of practice responses.

MARKING

  1. Mark strictly to the mark scheme.
  2. Marks awarded must relate directly to the marking criteria.
  3. The weightings for the assessment objectives are given in the specification.
  4. The inclusion of the command word "Discuss" in the question indicates that the Quality of Extended Response is being assessed.
Oxford Cambridge and RSA Examinations

J277/01

Mark Scheme

June 2026

Question Answer Marks Guidance
1 (a) Analogue [1]
Digital [1]
Sample Rate [1]
Hertz [1] 		4
  • Must be in the correct order to award marks.
  • Accept 'Hz' for Hertz.
1 (b) Row 1 (Binary): 00101011 [1]
Row 2 (Hex): AA [1]
Row 3 (Denary): 255 [1]
Row 3 (Binary): 11111111 [1] 		4
  • For Hex, accept 'aa' or 'Aa'.
  • For Binary, leading zeros are not required unless specified as 8-bit in Q.
1 (c) Answer: 10010011 [2]

Working marks:
- Evidence of correct binary addition method (e.g. carries shown) [1]
- Final correct answer [1] 		2
  • Full marks for correct answer with no working.
  • Follow through (FT) mark available if one calculation error is made but method is correct.
1 (d) Shift: 00110000 [1]
Effect: Multiplies by 4 [1] 		2
  • Reject "Multiplies by 2" (this is a 1 place shift).
  • Reject "Numbers move left" (must state the mathematical effect).
1 (e) Explanation:
- ASCII uses 7 bits (or 8 bits) per character / can represent 128 (or 256) characters [1]
- Unicode uses 16/32 bits per character / can represent over 1 million characters [1]
- Therefore Unicode can represent all languages/emojis, whereas ASCII is limited to English/Western text [1] 		2
  • Max 2 marks.
  • Award 1 mark for the difference in size (bits).
  • Award 1 mark for the difference in usage (languages/emojis).
Question Answer Marks Guidance
2 (a) Any two from:
- Switch [1]
- Router [1]
- Wireless Access Point (WAP) [1]
- Network Interface Card (NIC) [1] 		2
  • Reject "Cables" (stated in question).
  • Reject "Modem" (unless specifically linked to internet connection part).
2 (b) Any two benefits (2 marks per benefit - Point + Explanation):
- Speed: Wired connections usually offer higher bandwidth/speed [1] than wireless [1].
- Interference: Wired is less susceptible to interference from walls/other devices [1] making it more stable [1].
- Security: Harder to intercept data [1] as you need physical access to the cable [1]. 		4
  • Do not accept "Cheaper" without qualification (cabling a building is often expensive).
  • Answer must be a comparison (better than wireless).
2 (c) HTTP -> Transmits web pages... [1]
IMAP -> Retrieves emails... [1]
SMTP -> Sends emails... [1] 		3
  • All lines must be correct for full marks.
  • 1 mark for each correct link.
2 (d) 1. Browser sends URL to DNS [1]
2. DNS looks up IP address matching the URL [1]
3. Returns IP address to browser [1]
(Optional) If not found, asks another DNS server. 		3
  • Key concept: Converting URL to IP.
  • Max 3 marks.
Turn over

J277/01

Mark Scheme

June 2026

Question Answer Marks Guidance
3* Indicative Content:

Ethical Issues:
- Digital Divide: Those who cannot afford the tech miss out on lower premiums.
- Inaccuracy: If the device fails, premiums might go up unfairly.
- Pressure: Users may feel forced to share private data to save money.

Privacy Issues:
- Surveillance: Constant tracking of location and habits.
- Data Leakage: Risk of sensitive health data being hacked.
- Consent: Users may not understand how much data is being shared.

Legal Issues:
- Data Protection Act (2018): Data must be kept secure, accurate, and relevant.
- Health data is 'special category' data requiring explicit consent.
- Users have the right to request deletion of data. 		8 Levels of Response:
(See table below for marking criteria)

The mark is for the quality of the discussion, not just listing points.
Level Mark Description
Level 3 6–8 Precision: A line of reasoning is presented with detailed technical analysis.
Breadth: Covers Ethical, Privacy AND Legal issues comprehensively.
Terminology: Specialist terms (e.g. Encryption, DPA, GDPR) are used correctly.
Relevance: Directly addresses the "Health Insurance" scenario.
Level 2 3–5 Precision: A line of reasoning is presented with some analysis.
Breadth: Covers at least two areas (e.g. Ethics and Privacy).
Terminology: Some appropriate terminology used.
Relevance: Mostly relevant but may be generic at times.
Level 1 1–2 Precision: Basic points made with little analysis (list-like).
Breadth: Focuses on only one area or is very vague.
Terminology: Little or no specialist terminology.
Relevance: Generic answer (e.g. "Computers can be hacked").
0 0 No response or response worthy of credit.
Question Answer Marks Guidance
4 (a) Row 1: Keylogger / Spyware [1]
Row 2: Brute Force Attack [1]
Row 3: SQL Injection [1] 		3
  • Accept 'Spyware' for Row 1.
  • Reject 'Virus' or 'Malware' (too generic).
4 (b) - Monitors network traffic (incoming/outgoing) [1]
- Checks traffic against a set of rules/criteria [1]
- Blocks traffic that does not meet criteria [1] 		2
  • Max 2 marks.
  • Must mention 'Rules' or 'Criteria' for the second mark.
4 (c) Graphical User Interface / GUI [1] 1 Tick box question.
4 (d) - OS allocates a small amount of processor time (or time slice) to each process [1]
- OS moves instructions for active process into CPU/RAM [1]
- When time runs out, OS saves state of current process [1]
- Switches to next process very quickly giving illusion of simultaneous execution [1] 		4
  • Key concept: Allocating small bursts of CPU time.
  • Accept 'Time Slice' or 'Processor Time'.
4 (e) - Defrag reorganises files so they are stored contiguously (together) [1]
- This reduces the movement of the read/write head [1]
- Which reduces data access time / speeds up loading [1] 		3
  • Must link physical movement (read/write head) to speed for full marks.
Turn over

J277/01

Mark Scheme

June 2026

Question Answer Marks Guidance
5 (a) MAR: Holds the address [1] of the data/instruction to be fetched [1].
MDR: Holds the data/instruction [1] that has been fetched from memory [1]. 		4
  • MAR must link to 'Address'.
  • MDR must link to 'Data' or 'Instruction'.
5 (b)(i) Any two:
- Dedicated to one task [1]
- Built into a larger system [1]
- Limited resources (RAM/CPU) [1]
- Real-time operation [1] 		2 Reject "Small" (too vague).
5 (b)(ii) - ROM is non-volatile [1]
- The program needs to be retained when power is lost / The program doesn't change [1] 		2
5 (c) - Cache stores frequently used data/instructions [1]
- Cache is faster to access than RAM [1]
- Larger cache means CPU waits less for data from RAM, improving performance [1] 		3
Question Answer Marks Guidance
6 (a) Device: Magnetic HDD [1]
Justification (3 marks):
- Cost: HDD is cheaper per GB than SSD [1]
- Capacity: HDD typically offers larger capacities for archiving [1]
- Speed: High speed is not required for archiving/long term storage [1] 		4
  • If SSD chosen, max 2 marks ONLY if justification is about durability (dropping the drive).
  • Context of 'Archiving' points towards HDD.
6 (b) Calculation:
- 100 seconds (time) * 20,000 Hz (samples/sec) [1]
- * 16 bits (or 2 bytes) = 4,000,000 bytes [1]
- Convert to MB: 4,000,000 / 1,000,000 = 4 MB [1] 		3
  • Allow method marks if calculation error but logic correct.
  • Answer must be 4 MB.
6 (c) Any two drawbacks (2 marks per drawback):

1. Dependence on Internet [1]
- If the connection is lost/unstable, the editor cannot access/upload files. [1]

2. Slow Bandwidth/Upload [1]
- Transferring large video files takes much longer than a local drive. [1]

3. Security/Hacking Risks [1]
- If the server is breached, confidential client footage could be stolen. [1]

4. Ongoing Costs [1]
- Subscription fees over 10 years may be more expensive than buying a drive. [1] 		4
  • Award 1 mark for the valid point.
  • Award 1 mark for the expansion/explanation of why it is a drawback for this scenario.
Question Answer Marks Guidance
7 (a) - VM is a portion of secondary storage used as RAM [1]
- When RAM is full, idle programs are moved to VM [1]
- Moving data between RAM and HDD (swapping) is slow [1]
- Reduces overall performance / Causes 'thrashing' [1] 		4
7 (b) Choice: Client-Server [1]
Justification:
- Centralised backup / security [1]
- Files accessible from any computer [1] 		3
7 (c) Lossy Compression:
- Permanently removes data/quality to save space [1]
- Suitable for the uni if perfect quality isn't needed [1]

Lossless Compression:
- Retains all original data/quality [1]
- Files are larger than lossy [1] 		4
  • Must compare both types for full marks.
Total: 80 Marks