Computer Science 9618/11 October/November 2023: question paper and mark scheme

Mark scheme

1(a) 2 marks for all 3 lines correct 2 1 mark for 1 line correct Description Term a component created drawing list using a formula defines one characteristic drawing object of a component data required to create all property components in the graphic 1(b) 1 mark for the definition 3 • The number of bits used to represent each colour 1 mark for each bullet point for the explanation • Increase in bit depth means the image has a greater range of colours // Decrease in bit depth means the image has a smaller range of colours • Increase in bit depth makes the image closer to the original / more realistic // Decrease in bit depth makes the image less like the original / less realistic 1(c) 1 mark for each bullet point (max 2) 2 • Reduced bandwidth usage when transmitting the message • Reduced transmission time from email client to email server • Reduced storage space on the email • Email accounts often have a maximum size for an attachment

Mark scheme

2(a) 1 mark for each bullet point (max 3) 3 • Receives packets from internet / external network • Implements a firewall • Analyses the destination IP address of each packet • Forwards the packet towards its destination // send packets onto local network or external network • ...using the routing table • Maintains / updates the routing • Allocates private IP addresses • Finds the most efficient route to the destination • Changes the packet format for transmission over the next network // • Network Address Translation (NAT):NAT is a technique used by routers to allow multiple devices in a private local area network (LAN) to share a single public IP address. 2(b) Switch: 1 mark for each bullet point (max 1) 3 • To allow two or more devices to communicate with one another • To connect individual devices to each other • To receive transmissions and forward them to their destination Wireless Access Point (WAP): 1 mark for each bullet point (max 1) • To allow connection of devices (to the central device) using radio signals / Wi-Fi • To allow the central device to send / receive radio signals / Wi-Fi signals • To allow wireless enabled devices to connect to a wired network Bridge:1 mark for each bullet point (max 1) • To connect two LANs / segments with the same protocol • To transmit data between two networks with the same protocol 2(c) 1 mark for each bullet point (max 2) 2 • The students cannot access their files without a reliable internet connection • The amount of space for no payment may be limited so students will have to purchase more space if needed • The students do not have control over the backup (or security) of their work // the students are dependent on a third party for the (security and) backing up of their work 2(d) 1 mark for each advantage and 1 mark for valid corresponding expansion 2 • Star topology is more resilient to faults • …because there is no single cable and leads to less disruption to teaching • Higher performance as fewer collisions • ...because each device in the classroom is only connected to the switch • Easier to add new nodes • …because each device in the classroom connects directly to the switch • Easier to fault find compared to bus topology

Mark scheme

3(a) 1 mark for each correct relationship or relationships 3 • 1:M between CUSTOMER and SHOP_ORDER • 1:M between SUPPLIER and ITEM • 1:M between SHOP_ORDER and ORDER_ITEM and M:1 between ORDER_ITEM and ITEM SHOP_ORDER CUSTOMER ORDER_ITEM SUPPLIER ITEM 3(b) 1 mark for each bullet point (max 3) 3 • Reduced data redundancy • Improved data integrity / consistency / referential integrity • Allows for views / improved privacy • Allows for program-data independence • Complex queries can be executed 3(c)(i) 1 mark for 1 CREATE DATABASE SHOP; 3(c)(ii) 1 mark for each line (max 4) 4 Either: SELECT SUM(Quantity) FROM ORDER_ITEM, SHOP_ORDER WHERE ORDER_ITEM.OrderNo = SHOP_ORDER.OrderNo AND SHOP_ORDER.CustomerID = 'HJ231'; OR SELECT SUM(Quantity) FROM ORDER_ITEM (INNER) JOIN SHOP_ORDER ON ORDER_ITEM.OrderNo = SHOP_ORDER.OrderNo WHERE SHOP_ORDER.CustomerID = 'HJ231';

Mark scheme

4(a) 1 mark for each set of 4 rows (shaded) 2 A B C X 0 0 0 1 0 0 1 0 0 1 0 0 0 1 1 0 1 0 0 1 1 0 1 0 1 1 0 1 1 1 1 1 4(b) 1 mark for both AND gates 2 1 mark for NOT gate and OR gate and NOR gate

Mark scheme

5(a) 1 mark for identification of the register and 1 mark for role (max 2 for each 4 register) • Program Counter (PC) • stores the address where the next instruction is to be read from • Memory Address Register (MAR) • stores the address of the memory location (or an I/O component) currently being read from or written to • Current Instruction Register (CIR) • holds the instruction currently being decoded and/or executed • Status Register • Contains bits which can be referenced individually and set or cleared depending on the operation e.g. overflow, underflow 5(b) 1 mark for each bullet point (max 2) 2 • Immediate Access Store holds all the data / instructions / programs currently in use • Immediate Access Store is volatile memory • Immediate Access Store has fast access times 5(c)(i) 1 mark for each bullet point (max 1) 1 • The CPU can now perform nearly twice as many F-E cycles per second • Instead of 2.1 billion F-E cycles per second, the CPU can now perform 4 billion FE cycles per second 5(c)(ii) 1 mark for each bullet point (max 5) 5 • Multiple cores introduce additional overheads • …because of the need for communication between cores • Software may not be designed for multiple cores… • …so one of the cores will be left idle • Memory access speed may not match speed of cores… • …so causing delay • The two computers may have more differences than just the cores • …one may have more RAM which allows faster multitasking • ...one may have a GPU • ...etc.

Mark scheme

6(a) 1 mark for each bullet point (max 4) 4 • easier to debug the program • … because it translates line-by-line and stops when an error is found whereas the compiler translates all the program at the same time • … only reporting one error at a time • … which allows the error to be corrected in real time whereas the program would need to be corrected and recompiled • ... and the program can restart at same point when error occurred with a compiler the program needs to be re-run • The effect of any changes made by the programmer can be seen immediately with a compiler the effects can only be seen after re-running • A partially completed program can be translated / tested on its own a compiler cannot translate a partial program 6(b) 1 mark for each bullet point (max 1) 1 • Partially compiled programs can be used on different platforms as they are interpreted when run • Code is optimised for the CPU as machine code is generated at run time • Source code does not need recompiling so more efficient to run 6(c)(i) 1 mark for each bullet point (max 2) 2 • Prettyprint • Expand/collapse code blocks • Auto indentation / formatting 6(c)(ii) 1 mark for each bullet point (max 2) 2 • Single stepping • Breakpoints • Report window • Variable expressions

Mark scheme

7(a) 1 mark for each bullet point (max 3) 3 Generic mark points: • Additive manufacturing • Uses a digital 3D model or a Computer Aided Design (CAD) (file) • Builds up the model one layer at a time • ...starting from the bottom • ...using x, y and z co-ordinates • The material is fused / cured together layer by layer Specific mark points: 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) • Uses liquid plastic resin melted with arc lamps Selective Laser Sintering (SLS) • Uses a laser to form objects from powdered material 7(b) 1 mark for each bullet point (max 2) 2 • To prevent overheating // ensure material is hot enough • ...by identifying the temperature of the object (being printed) • ...by identifying the temperature of the material being used 7(c) 1 mark for each bullet point (max 2) 2 • Dynamic RAM has lower cost per unit • A fast access speed is not needed • Higher bit density // more data can be stored per chip

Mark scheme

8(a) 1 mark for: 1 • To create a symbol table 8(b)(i) 1 mark for each bullet point 3 • Data movement: e.g. LDR #50 // STO 201 • Arithmetic operation: e.g. ADD 100 // INC IX • Conditional instruction: e.g. JPE 96 8(b)(ii) 1 mark for each bullet point (max 2) 2 Similarity: • both load the contents of an address into the Accumulator Difference: • direct accesses the address given by the operand whereas indexed adds the contents of IX to the operand and accesses the data at that calculated address 8(b)(iii) 1 mark for 1 • Indirect (addressing) • Relative (addressing) 8(c)(i) 0000 0101 1 8(c)(ii) 0000 0010 1 8(c)(iii) 1101 0010 1

Mark scheme

9(a) One mark for each bullet point (max 2) 2 • Feedback ensures that a system operates within set criteria / constraints • ...by enabling system output to affect (subsequent) system input • ...thus allowing conditions to be automatically adjusted 9(b) One mark for each reason to max 3 to match the example given 3 • Dedicated to one task applied to example • Does not require much processing power applied to example • Built into a larger system applied to example • Contains firmware that cannot be easily updated applied to example • The system does not have its own operating system • An embedded system must contain a processor, memory and an I/O capability // Dedicated hardware