Computer Science 9618/11 October/November 2025: question paper and mark scheme

Mark scheme

1(a)(i) B3A 1 1(a)(ii) 0001 0000 1000 1 1(a)(iii) 1 mark for the working 2 1 mark for the correct denary value Working: Method 1: 1111 1011 1100 Flip the bits 0000 0100 0011 Add 1 0000 0000 0001 + 0000 0100 0100 Method 2: -2048 + 1024 + 512 + 256 + 128 + 32 + 16 + 8 + 4 // -128 + 32 + 16 + 8 + 4 Denary value: -68 1(b)(i) (1) 00101011 1 1(b)(ii) 1 mark per bullet point, max 2 marks 2 • An overflow error occurs • The answer cannot be represented in the number of bits available // The answer is larger than the maximum positive number that can be stored in the register // The answer is smaller than the most negative number that can be stored in the register

Mark scheme

2(a) 1 mark for each correct relationship, max 2 marks 2 2(b) 1 mark per bullet point, max 2 marks 2 • There are no repeating groups of attributes • There are no many-to-many relationships • There are no partial key dependencies // no non-key dependencies // no transitive dependencies 2(c)(i) 1 mark per bullet point, max 2 marks 2 • DELETE FROM and correct table • Correct condition Example answer: DELETE FROM PLACEMENT WHERE Complete = TRUE; 2(c)(ii) 1 mark per bullet point, max 4 marks 4 • SELECT COUNT any appropriate field • AS and an appropriate name • FROM and correct table and WHERE and one correct condition • Two AND clauses with the other two correct conditions Example answer: SELECT COUNT (CompanyID) AS TotalPlacements FROM PLACEMENT WHERE CompanyID = "NEAM" AND StudentID = "LDEA01" AND Complete = TRUE; 2(d) 1 mark per bullet point, max 3 marks 3 Generic mark points (max 2) • Referential integrity ensures that related data is consistent • Referential integrity ensures that every foreign key has a corresponding primary key • Referential integrity provides for cascading update / delete • Referential integrity ensures that if a primary key is deleted or modified all linked records in foreign table will be deleted or modified // Referential integrity stops "orphaned records"—records in a table that point to an entry in another table that no longer exists Specific mark points (max 2) for good examples e.g. • CompanyID is a foreign key in PLACEMENT table and is dependent on the primary key CompanyID in COMPANY table • If a record is deleted from the STUDENT table, then all records with the same StudentID will be deleted from the PLACEMENT table • If a CompanyID is modified in the company table, all records with that CompanyID in the placement table will also be modified

Mark scheme

3(a) One mark per bullet point, max 2 marks 2 • (A NAND B) and (NOT A OR NOT C) • XOR and NOT 3(b) 1 mark per bullet point, max 2 marks 2 • One correct term: (R AND S AND NOT T) // (NOT R AND NOT S AND T) • Second correct term plus the OR in correct place Answer: Q = (R AND S AND NOT T) OR (NOT R AND NOT S AND T)

Mark scheme

4(a) 1 mark for: 1 LSL #2 4(b) 1 1 1 1 0 0 0 1 1 4(c) 1 0 0 1 0 0 0 1 1 4(d) 1 1 1 1 1 0 0 1 1

Mark scheme

5(a)(i) 1 mark per bullet point, max 2 marks 2 • Installs driver software for devices connected to external ports • Manages communication between devices • Manages hardware interrupts 5(a)(ii) 1 mark per bullet point, max 2 marks 2 • Prevents unauthorised access • ... by providing authentication // by validating users and processes • Implements access rights and permissions • Makes provision for recovery of lost data • Carries out Operating System security updates as available • Carries out auditing and keeps logs of activity 5(b)(i) One mark for benefit, one mark for appropriate matching expansion 2 e.g. • Less code needs to be developed as code is pre-written • … thereby reducing the time to write a program • The library routine will be pre-tested and documented • ... reducing the time taken to test a program // giving confidence that the routine works as it should • The code for the library routine can written in a different programming language • … which allows the use of special features of that language • The user’s source code is more readable • ... as the library routine is simply called in the source code rather than being written out in full • The library could contain the code for complex routines • ... thus allowing the programmer to include modules they might not be able to code 5(b)(ii) 1 mark for drawback, 1 mark for appropriate matching expansion 2 e.g. • Compatibility issues • … the library routine may not work with current program • Not guaranteed to be thoroughly tested • ... there could be unexpected problems (bugs/virus) • The library routine may not match needs exactly // The library routine may give unexpected results • … so it will need to be edited and tested • If the library routine is later edited or changed (by someone else) • … there could be unexpected errors or results 5(c) 1 mark per bullet point, max 2 marks 2 • Prettyprint • Expanding and collapsing code blocks • Automatic / smart indentation / formatting

Mark scheme

6(a) 1 mark for each correct description, max 2 marks 2 Register Role stores the intermediate results of arithmetic and logical ACC operations // holds the result of a calculation CIR holds the instruction currently being decoded and/or executed 6(b) 1 mark per bullet point, max 2 marks 2 e.g. • Latency may be increased • … because the cores must communicate with one another • There is a potential for dead-lock situations • … where one core may wait for information from other cores which in turn are waiting for the first one • Not all software is designed to use multi-cores • ... so some of the additional cores would be idle • Increased heat generation • ... which could cause damage to other components 6(c) 1 mark per bullet point, max 3 marks 3 • DRAM requires to be refreshed/charged SRAM does not request a refresh • DRAM stores each bit as charge SRAM uses flip-flop to store each bit • DRAM is less expensive to manufacture SRAM is more expensive to manufacture • DRAM has slower access speeds SRAM has faster access times • DRAM has higher storage/bit/data density SRAM has lower storage/bit/data density • DRAM is used in main memory SRAM is used in cache

Mark scheme

7(a) 1 mark for each correct description, max 2 marks 2 Type of IP Description address IP address that does not change each time a device Static connects to the network IP address assigned to a device on a network to allow the Public device to be visible on the internet 7(b) 1 mark per bullet point for justification, max 2 marks 2 Choice: Invalid (no mark for the choice) Justification: • It is not IPv4 because the maximum denary value should be 255, this uses 256 • It is not IPv6 because it uses a full stop to separate sections and not colon // It is not IPv6 because there are not enough groups 7(c) 1 mark per bullet point, max 4 marks 4 • The browser checks its cache for the URL • The browser parses the URL and splits it into its component parts • The browser finds the IP address for the domain name by querying a DNS server • The browser receives the matching IP address from the DNS server • The browser creates connection with the web server with the matching IP address • A request for the resource is sent to the web server with that IP address • The browser renders and displays the result • The IP address is stored in the browser cache for future use 7(d)(i) 1 mark for the working 2 1 mark for the correct answer Working: (512 * 2048 * 8) / (8 * 1024 ) // (512 * 2048) / 1024 // (29 * 211 * 23) / (23 * 210) // (29 * 211) / 210 Answer: 1024 kibibytes // 2 10 kibibytes 7(d)(ii) 1 mark per bullet point, max 2 marks 2 • The file will contain metadata • The file will have a header 7(d)(iii) 1 mark per bullet point, max 2 marks 2 • Sequences of consecutive identical colours / pixels • ... are stored as the colour value and the number of times it occurs consecutively

Mark scheme

8(a) 1 mark for each correct explanation, max 2 marks 2 Virus: Malicious program/software that replicates/copies itself and deletes/alters files/data stored on a computer Pharming: Malicious code/software installed on a computer which redirects user to a fake website to obtain personal data 8(b) 1 mark per bullet point, max 3 marks 3 e. g. • Students should consider privacy issues • Students should not make inappropriate use of social networking // Students should not engage in cyberbullying • Students should not copy work that is not their own • Students should abide by the school rules/guidelines for accessing the network • Students should only use the school network for legitimate purposes • Students should not hack / crack other computers 8(c) 1 mark per bullet point, max 4 marks 4 e. g. Negative Impacts • If students use AI to shortcut learning, they may miss out on developing reasoning and problem-solving skills // Students may not be learning anything // It could lead to a decline in specific skills • It could have negative impacts on student communication // heavy reliance on AI may limit opportunities for collaboration, teamwork, and face-to-face communication • Emphasises the digital divide// some students may not have access to the technology • The AI answer might not be correct leading to mis-information • Increased screen time and isolation could contribute to anxiety or loneliness Positive Impacts • Students given additional support may do better • Pupils who struggle in traditional settings may gain self -esteem through AI-assisted learning at their own pace Long-Term Impacts • Protection of intellectual property // ethical issues and considerations • Schools may need to redesign curricula and/or assessment to integrate AI

Mark scheme

9 1 mark per bullet point, max 3 marks 3 • Monitoring systems do not take any action whereas control systems act autonomously to change the environment if the values are out of a prescribed range • Control systems use actuators monitoring systems do not have any actuators • Control systems make use of feedback monitoring systems do not make use of feedback • The output from a monitoring system does not affect the subsequent input whereas output from a control system affects the next input.

Mark scheme

10(a) 1 mark per bullet point, max 3 marks 3 Generic mark points: (max 3) • Additive manufacturing • Uses a digital file created from 3D modelling software or Computer Aided Design (CAD) software • The printer builds up the model one layer at a time • The process is repeated for each layer • Some materials may need time to cool and set or UV curing using LEDs for photopolymer resins Specific mark points: (max 1) e.g. • Fused Deposition Modelling (FDM) // Material is heated and pushed through nozzle / extruder • Stereolithography (SLA) // Photosensitive liquid resin is exposed to a UV- laser beam • Digital Light Processing (DLP) // Photosensitive liquid resin is exposed to a UV projected image of the layer to cure the resin • Selective Laser Sintering (SLS) // Uses a laser to form objects from powdered material, the material can be plastics or metals 10(b) 1 mark 1 • To free up the processor to carry out other tasks as the rate data is received by the printer is different from the rate at which it can be processed • To manage the mismatch in speed between the processor and the peripheral / 3D printer