Mark Scheme: J277/01 Computer Systems (Version F)

QAnswer/Indicative ContentMarks
1.1 Fetch-Execute Cycle: (1 mark per point, max 4)
- Fetch: The CPU fetches the next instruction from RAM using the address in the Program Counter. (1)
- Decode: The instruction is decoded by the Control Unit into commands the CPU understands. (1)
- Execute: The command is carried out (e.g. calculation by ALU or data movement). (1)
- The cycle repeats. (1)
4
1.2 ALU: Performs arithmetic (e.g. +,-,*,/) and logic operations (e.g. AND, OR). (2)
CU: Sends control signals to coordinate the movement of data through the CPU. (1)
3
1.3 Performance: Clock speed isn't the only factor (1). Cache size/speed and number of cores also limit performance (1). The system might be bottlenecked by slow RAM or Storage (1). 3
2.1 Bit, Nibble, Byte, Kilobyte, Megabyte, Gigabyte, Terabyte, Petabyte (2).
Nibble is 4 bits (1), Byte is 8 bits (1).
4
2.2 16GB = 16,000MB (1). 16,000 / 2 = 8,000 files (1).
(Accept 16,384MB / 2 = 8,192 files if base-2 used). (6 marks for steps: showing conversion, division, units).
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3.1 Binary to Denary: 10101010 = 170 (1). 11110000 = 240 (1). 00001111 = 15 (1). 3
3.2 Binary to Hex: 1010 = A (1). 1111 = F (1).
Denary to Hex: 31 = 1F (2).
4
3.3 Addition result (2). Overflow description: When the result of an addition requires more bits than the CPU has registers for (e.g. 9th bit in an 8-bit system). (2) 4
3.4 Left shift 2: 00001100 -> 00110000 (2). Effect: Value is multiplied by 4. (2) 4
4.1 Each pixel is assigned a unique binary code (1) representing its color (1). The codes are stored in order to form the image grid (2). 4
4.2 Resolution, dimensions, color depth, GPS location, date/time, file type. (1 mark each, max 3). +1 for definition. 4
4.3 Increasing color depth means more bits per pixel (1). This increases the total number of bits needed to store the image (1), thus increasing file size (2). 4
5.1 Reduces bandwidth usage (1). Faster loading/buffering (1). Less storage space needed on the server (1). 3
5.2 Lossy: Data is removed to reduce size, non-reversible (2).
Lossless: Data is compressed without losing anything, reversible (2).
Mandatory: Text files, programs, spreadsheet data (any data where 100% accuracy is needed). (2)
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5.3 Cloud: Scalable, accessible anywhere, low upfront cost (2).
Local: Control over security, no internet needed, one-time cost (1).
3
6.1 WAP: Provides a wireless connection point for devices (2).
NIC: Hardware inside a device that allows it to connect to a network (3).
5
6.2 Brute-force: Attempting every password combination (2).
Prevention: Locking the account after X failed attempts prevents further guesses (3).
5
7 L3 (7-9 marks): Comprehensive balanced discussion. Covers Privacy (surveillance, tracking) vs Security (crime prevention, safety). Accurate legal references (DPA/GDPR). Clear conclusion.
L2 (4-6 marks): Good understanding but may focus more on one side. Some legal mention.
L1 (1-3 marks): Basic points about cameras/privacy.
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