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Cambridge AS & A Level Computer Science (9618), Paper 1 Theory Fundamentals, October/November 2025. Read both free below, or download them. Done the paper? Get it marked by AI against this mark scheme.
9618_w25_qp_129618_w25_ms_129618/12/O/N/25
Each question as it's printed, and the mark scheme's points for it, as text. Diagrams, tables and graphs are in the PDFs above.
Question
Draw one line from each verification method to indicate whether it is used during data transfer or data entry. Verification Method Use Parity byte check Checksum Data transfer Visual check Data entry Parity block check [2]
Mark scheme
1 1 mark for 2 or 3 correctly connected verification method boxes, 2 marks for 2 all 4 correct Verification Method Use Parity byte check Checksum Data transfer Visual check Data entry Parity block check
Question
(a) Complete the table by describing each term. Term Description Copyright …… Open Source (Initiative) Shareware …… Software Licence …… [4] * 0000800000003 * DFD 3 (b) Describe the purpose of a code of conduct. …… [2]
Mark scheme
2(a) 1 mark for each correct row, max 4 marks 4 Term Description Copyright Gives the holder the legal right of ownership of intellectual property Open Source Software can be freely copied, distributed or (Initiative) adapted Shareware Gives the user a trial period / limited functionality before a payment/sign up may be required Software A (legal) agreement that defines the rights and Licence terms of usage for the software 2(b) 1 mark per bullet point, max 2 marks 2 e.g. • to create a safe, respectable and professional working environment for all employees • to ensure that employees understand the expectations • ... and the consequences of their actions • to provide a clear outline of what is considered good practice • so there are clear rules to follow in certain situations • to protect the reputation of the organisation // maintain public trust
Question
(a) (i) State what is meant by relative addressing. …… [1] (ii) Registers such as the Accumulator (ACC) and the Index Register (IX) are used in the CPU. Identify two special purpose registers used in the CPU. Do not include the ACC or IX in your answers. 1 …… 2 …… [2] * 0000800000004 * DFD 4 (b) The following table shows part of the instruction set for a processor. The processor has two registers: the ACC and an IX. Instruction Explanation Opcode Operand LDM #n Immediate addressing. Load the number n to ACC LDD <address> Direct addressing. Load the contents of the location at the given address to ACC LDI <address> Indirect addressing. The address to be used is at the given address. Load the contents of this second address to ACC LDX <address> Indexed addressing. Form the address from <address> + the contents of the index register. Copy the contents of this calculated address to ACC LDR #n Immediate addressing. Load the number n to IX <address> can be an absolute or symbolic address # denotes a denary number, e.g. #127 The current contents of the main memory and the index register are shown. Address Instruction 98 8 99 16 100 3 101 98 102 32 IX 2 Write the contents of the ACC after each instruction is executed. Instruction Value in ACC LDM #98 LDI 101 LDX 100 [3] * 0000800000005 * DFD 5 (c) A student buys a new computer. The table shows the specifications of the old computer and the new computer. Old computer New computer 1.8 GHz dual core processor 2.3 GHz dual core processor 16 MB cache 32 MB cache Explain why increasing the clock speed and increasing the cache memory will improve the performance of the computer. Clock speed …… Cache memory …… [4] * 0000800000006 * DFD 6
Mark scheme
3(a)(i) 1 mark 1 • The value of the operand is an offset value which is added to another base value to give the address from which the contents are loaded to the accumulator 3(a)(ii) 1 mark per bullet point, max 2 marks 2 • Program counter (PC) • Memory Data Register (MDR) • Memory Address Register (MAR) • Current Instruction Register (CIR) • Status Register 3(b) 1 mark for each correct value, max 3 marks 3 Instruction Value in ACC LDM #98 98 LDI 101 8 LDX 100 32 3(c) 1 mark per bullet point, max 2 marks for each 4 Clock Speed: • Processor can perform more F-E cycles per second • ... so more instructions / data can be processed each second Cache Memory: • Can store more of the most frequently used instructions • … which reduces the need to access slower RAM
Question
A relational database, SHIPPING, stores data about the ships in a company and the containers that are carried on the ships. The database has the following tables: CONTAINER(ContainerID, Type, Weight, OwnerName, ShipID) SHIP(ShipID, Type, Capacity, ShipName) (a) Describe the relationship between the two tables. Refer to the primary and foreign keys in your answer. …… [2] (b) The table CONTAINER needs an additional field to store the data for the last inspection date. Write a Structured Query Language (SQL) script to add one field to the table CONTAINER to store the date of last inspection of the container, for example 08/07/2019. …… [2] (c) Write an SQL script to return the number of containers stored in the database for the ship with the name Caledonia. …… [4] * 0000800000007 * DFD 7 (d) Describe the purpose of a developer interface in a Database Management System (DBMS). …… [2] * 0000800000008 * DFD 8
Mark scheme
4(a) 1 mark per bullet point, max 2 marks 2 • The relationship between SHIP and CONTAINER is one-to-many (1:M) • The primary key ShipID in the SHIP table is linked to the foreign key ShipID in the CONTAINER table 4(b) 1 mark per bullet point, max 2 marks 2 • ALTER TABLE statement • Including the additional field with a suitable field name and suitable field type Example answer ALTER TABLE CONTAINER ADD InspectionDate DATE; 4(c) 1 mark per bullet point, max 4 marks 4 • SELECT COUNT statement • Using the correct tables • Joining the tables • The condition for the name Example Answer 1: SELECT COUNT(ContainerID) FROM CONTAINER, SHIP WHERE CONTAINER.ShipID = SHIP.ShipID AND ShipName = "Caledonia"; Example Answer 2: SELECT COUNT(ContainerID) FROM CONTAINER INNER JOIN SHIP ON CONTAINER.ShipID = SHIP.ShipID WHERE ShipName = "Caledonia"; 4(d) 1 mark per bullet point, max 2 marks 2 • To allow the user to create / modify / delete tables // maintain the database • To allow the user to set up / modify relationships • To allow the user to create a form for data input • To allow a user to add tools to a form // for example, drop-down boxes / buttons etc. • To allow a user to design a report (to show the output in an organised manner) • To allow a user to add a menu to enable a choice of different actions • To allow a user to inspect the database contents and metadata • ... by creating and/or running different SQL queries
Question
A local area network (LAN) has five computers, one switch and one server. (a) Describe the characteristics of a LAN. …… [2] (b) Complete the following diagram to show how these devices are connected in a star topology. Computer Computer Computer Computer Computer Server Switch [2] (c) Describe how packets are transmitted between two hosts using a star topology. …… [3] * 0000800000009 * DFD 9 (d) Another type of network is a bus network. Ethernet is used to transmit and receive data between the devices on the bus network. Describe how collisions are detected and managed on this network. …… [3] (e) Complete the table by identifying one threat to computer and data security posed by networks and the internet. Describe the threat and give a method of prevention. Threat Description Prevention [3] * 0000800000010 * DFD 10
Mark scheme
5(a) 1 mark per bullet point, max 2 marks 2 • Covers a small geographical area • Normally privately owned / dedicated infrastructure • Can use wired or wireless communication 5(b) 1 mark per bullet point, max 2 marks 2 • All computers directly connected to switch and no other connections • Switch connected directly to server 5(c) 1 mark per bullet point, max 3 marks 3 • The sending device sends the packets to the switch • The switch checks the destination address on each packet • … and sends them only to the intended receiver 5(d) 1 mark per bullet point, max 3 marks 3 • The use of CSMA/CD // Carrier Sense Multiple Access with Collision Detection • The workstations listen to the communication channel • ... and send data only when there is no data being transmitted / the line is idle • If a collision is detected, transmission is aborted • …and a jamming signal is sent • The workstation calculates a random wait time before trying to re-transmit • The random time is increased if there are multiple collisions 5(e) 1 mark for correct threat 3 1 mark corresponding description 1 mark for correct method of prevention Threat Description Prevention Malware / Malicious code that can Anti-virus // Anti- Virus alter/delete files malware // Firewall Spyware Records keystrokes which are Anti-spyware // sent to third party Firewall // Anti- malware Hacking Gaining unauthorised access to Authentication // a computer network / device Firewall Phishing Emails supposedly from Use a spam filter // reputable companies are sent to Do not open emails trick people into revealing from unknown personal information sources Pharming Users are directed to a bogus Use a VPN // Anti- website that looks legitimate to malware// Do not obtain personal information open links or download attachments
Question
(a) A sound file is compressed by reducing the sampling rate. State whether this is lossless or lossy compression. Justify your choice. Type of compression …… Justification …… [1] (b) The following table shows some words and corresponding denary values. Word Denary value Computing 55 Science 56 Computers 57 are 58 Brilliant! 59 is 60 Fun! 61 Amazing! 62 The following table shows three bytes of data that have been received. Use the table to find the corresponding words from the binary values received. Binary value 00111000 00111100 00111110 Word Working …… [1] * 0000800000011 * DFD 11 (c) A computer system uses even parity. The least significant (rightmost) bit of each byte is the parity bit. (i) Complete the byte by writing the missing parity bit: parity bit 0 1 0 1 1 1 0 [1] (ii) The computer also uses parity block check. The parity block check uses even parity. Computer A transmits four bytes of data to computer B, followed by a parity byte. Computer B receives the following sequence of bytes. parity bit 1 0 1 1 0 1 1 1 0 1 1 1 0 0 0 0 0 0 0 1 1 0 1 1 0 1 1 1 0 1 0 0 parity byte 1 0 1 0 0 0 0 0 Following transmission, one of the four bytes of data has an error in one of the bits. Circle the bit that has been altered during the data transfer. [1] (d) A bitmap image has a resolution of 1000 pixels wide by 2000 pixels high. The colour depth is 16 bits. Calculate an estimate of the file size in megabytes. Show your working. File size …… megabytes [2] * 0000800000012 * DFD 12
Mark scheme
6(a) 1 mark for correct answer 1 Type of compression: lossy Justification: There will be fewer samples per second, so data will be permanently lost // There will be fewer samples per second, so the original sound cannot be re - created 6(b) 1 mark for correct words in the correct order 1 Binary Value 0011 1000 0011 1100 0011 1110 Word Science is Amazing! 6(c)(i) 1 mark for correct answer 1 parity bit ↓ 0 1 0 1 1 1 0 0 6(c)(ii) 1 mark for correct answer 1 parity bit ↓ 1 0 1 1 0 1 1 1 0 1 1 1 0 0 0 0 0 0 0 1 1 0 1 1 0 1 1 1 0 1 0 0 parity byte→ 1 0 1 0 0 0 0 0 [1] 6(d) 1 mark for the working 2 1 mark for the correct answer Working: (1000 * 2000 * 16) / (8 * 1000 * 1000) // (1000 * 2000 * 2 / (1000 * 1000) Answer: 4 megabytes
Question
(a) The following binary addition is performed using 8‑bit registers. Complete the calculation using binary addition. 10000111 +00111001 [1] (b) A computer uses the Unicode character set. State the number of bits used to store one character from the Unicode character set. …… [1] (c) ASCII is another character set. The ASCII value for the character ‘h’ has the denary value 104. (i) Write the Binary Coded Decimal (BCD) value for the ASCII character ‘h’. …… [1] (ii) Write the hexadecimal value for the ASCII character ‘h’. …… [1] * 0000800000013 * DFD 13
Mark scheme
7(a) 1 mark for the correct answer 1 1100 0000 7(b) 1 mark for the correct answer 1 8 // 16 // 32 // 64 7(c)(i) 1 mark for the correct answer 1 0001 0000 0100 7(c)(ii) 1 mark for the correct answer 1 68
Question
A restaurant accesses software and stores data using cloud computing. (a) (i) Give two benefits of storing data using cloud computing. 1 …… 2 …… [2] (ii) Give two drawbacks of using cloud computing. 1 …… 2 …… [2] (b) The restaurant uses touchscreens as input devices to allow staff to select items from a menu. (i) Explain how a touchscreen converts the point of touch to a selection from the menu. …… [4] (ii) The image files that are displayed on the touchscreen have been corrupted. Identify two examples of utility software that could be used to recover the images. 1 …… 2 …… [2] * 0000800000014 * DFD 14
Mark scheme
8(a)(i) 1 mark per bullet point, max 2 marks 2 • Cloud storage can be free of charge for a limited amount • There is no need for personal storage devices • The data can be accessed from any computer with an internet connection • Cloud data services usually include data backup and recovery services • It is easier to share data / collaborate with colleagues • Cloud storage capacity can be quickly and easily increased if needed 8(a)(ii) 1 mark per bullet point, max 2 marks 2 • The storage/cloud can only be accessed with an internet connection • There may be no backups // possibly no control over backups // reliance on third party for backups • Uploading / downloading data could take a long time • Potential issues with the cloud storage company impacting access e.g. downtime or technical problems • Potential compatibility issues if wanting to move the data • Limited storage availability without paying extra • … meaning (possibly) more expensive in the long term • Possibly security issues 8(b)(i) 1 mark per bullet point, max 4 marks 4 Methods to determine point of touch (Max 2) • Resistive // two layers of material make contact and complete a circuit • Capacitive // contact with the screen creates a change in charge • Infrared // the beams are broken by the pointing device • Optical imaging // a shadow is created when the surface is touched • Acoustic pulse // the acoustic wave is absorbed by the pointing device • Selection from the menu (Max 2) • The point of touch is used to determine the x and y coordinates • The menu item corresponding to the coordinate position is recognised and the menu item is added to the order 8(b)(ii) 1 mark per bullet point, max 2 marks 2 • Disk repair / disk contents analysis • Back-up software
Question
(a) Consider the following logic circuit: A X B C Write the logic expression for the logic circuit. Do not simplify the expression. X = …… [2] (b) Consider the following logic expression: X = NOT ((A NAND B) XOR (NOT A OR NOT C)) A truth table for the logic expression is given: Row number A B C X 1 0 0 0 1 2 0 0 1 0 3 0 1 0 1 4 0 1 1 0 5 1 0 0 1 6 1 0 1 0 7 1 1 0 1 8 1 1 1 1 There are three errors in the truth table. Identify the three errors in the truth table by writing the row numbers with an incorrect output. Error 1 Row number …… Error 2 Row number …… Error 3 Row number …… [2] * 0000800000015 * DFD 15
Mark scheme
9(a) 1 mark per bullet point, max 2 marks 2 • NOT (A XOR B) • NAND ((B AND C) OR A) X = (NOT (A XOR B)) NAND ((B AND C) OR A) // X = ((B AND C) OR A) NAND (NOT (A XOR B)) 9(b) 1 mark for 1 or 2 row numbers correct, 2 marks all three correct 2 Row 2 Row 4 Row 7
Question
A programmer is developing a computer program. (a) Explain how the programmer can first use an interpreter and then a compiler to develop the computer program. Interpreter …… Compiler …… [4] (b) The programmer releases the program as Free Software. Describe what is meant by Free Software. …… [2] (c) A user downloads the computer program from the internet. State what should be included as part of the download to make sure the program is authentic. …… [1] * 0000800000016 * DFD 16
Mark scheme
10(a) 1 mark per bullet point, max 4 marks 4 Max 2 from each section. Interpreter: • Use an interpreter while writing/coding the program • … to test / debug the partially completed program • … because errors can be corrected and processing continue from where the execution stopped // errors can be corrected in real time // errors are identified one at a time Compiler: • Use the compiler after the program is complete • … to create an executable file so source code not seen • Use the compiler to repeatedly test the same completed section without having to re-interpret every time 10(b) 1 mark per bullet point, max 2 2 • The software is free of restrictions • The software is not necessarily free of charge • The source code comes with the program // A user can edit the source code to add functionality / suit their needs • Users can share the software with others 10(c) 1 mark for a correct answer 1 • Digital Signature
Question
An automated system opens doors when a person is detected within 2 metres. The system closes the doors when there is no longer a person within 2 metres. Identify whether the automated system is an example of a monitoring system or a control system. Justify your choice. Monitoring or Control …… Justification …… …… [3]
Mark scheme
11 1 mark per bullet point, max 3 marks 3 Identification: Control system (no mark) Justification: • The system uses an actuator to open or close the doors • The output / opening the doors allows people to move, which changes the input to the sensor • The system acts autonomously on the feedback from a sensor
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Mark my 9618/12Examiners follow the generic marking principles at the front of the scheme, then each question's points: method (M), accuracy (A) and independent (B) marks, error carried forward where the scheme allows it, and positive marking, so you're credited for what you got right.
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On this page, free: the mark scheme for AS & A Level Computer Science 9618/12, October/November 2025 (9618_w25_ms_12), and the question paper (9618_w25_qp_12), to read or download, with each question's marking points written out underneath.
Computer Science 9618/12 for October/November 2025 is out of 75 marks, with 1 hour 30 minutes to answer it.
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