Cambridge A Level Computer Science 9608 — 2019 May/June Paper 1 · Variant 2

This document consists of 13 printed pages and 3 blank pages. DC (SC) 163549/4 © UCLES 2019 [Turn over Cambridge Assessment International Education Cambridge International Advanced Subsidiary and Advanced Level * 0 2 5 0 7 8 0 7 6 8 * COMPUTER SCIENCE 9608/12 Paper 1 Theory Fundamentals May/June 2019 1 hour 30 minutes Candidates answer on the Question Paper. No Additional Materials are required. No calculators allowed. READ THESE INSTRUCTIONS FIRST Write your centre number, candidate number and name in the spaces at the top of this page. Write in dark blue or black pen. You may use an HB pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Answer all questions. No marks will be awarded for using brand names of software packages or hardware. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. The maximum number of marks is 75.

2 9608/12/M/J/19 © UCLES 2019 1 Computers on the Internet have IP addresses. (a) IP addresses can be in either IPv4 or IPv6 format. (i) Give an example of a valid IPv4 address. … … [1] (ii) State why there is a need for IPv6 addressing. … … [1] (iii) A computer’s IPv6 address is: C100:2235::1000:25AA:AA50 Explain why this IPv6 address would be an invalid IPv4 address. … … … … [2] (b) A company has computers in two separate buildings that communicate using the Internet over a Public Switched Telephone Network (PSTN). (i) Describe the transmission of data using a PSTN. … … … … [2] (ii) The company wants to install a dedicated line between the two buildings. Identify one benefit and one drawback of installing a dedicated line between the two buildings. Benefit … … Drawback … … [2]

3 9608/12/M/J/19 © UCLES 2019 [Turn over (c) A network can use routers and gateways. Explain the role of routers and gateways in a network. … … … … … … … … [4] (d) The company has an email server. Identify three other types of server. 1 … 2 … 3 … [3]

4 9608/12/M/J/19 © UCLES 2019 2 Biyu is writing a computer program in a high-level language. (a) Biyu uses a language translator. (i) State the purpose of a language translator. … … [1] (ii) Biyu uses an interpreter. State two benefits of Biyu using an interpreter instead of a compiler while writing the program. 1 … … 2 … … [2] (iii) Name a translator other than an interpreter and a compiler. … [1] (b) Biyu uses library files in the program. Explain why software is often developed using library files. … … … … [2]

5 9608/12/M/J/19 © UCLES 2019 [Turn over 3 The fetch-execute cycle is shown in register transfer notation. 01 MAR [PC] 02 PC [PC] - 1 03 MDR [MAR] 04 CIR [MAR] (a) There are three errors in the fetch-execute cycle shown. Identify the line number of each error and give the correction. Line number … Correction … Line number … Correction … Line number … Correction … [3] (b) A processor’s instruction set can be grouped according to their function. For example, one group is the input and output of data. Identify two other groups of instructions. 1 … … 2 … … [2]

6 9608/12/M/J/19 © UCLES 2019 (c) The following table shows assembly language instructions for a processor which has one general purpose register, the Accumulator (ACC), and an Index Register (IX). Instruction Explanation Op code Operand LDM #n Immediate addressing. Load the denary number n to ACC LDD <address> Direct addressing. Load the contents of the location at the given 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 denary number n to IX STO <address> Store contents of ACC at the given address ADD <address> Add the contents of the given address to ACC INC <register> Add 1 to the contents of the register (ACC or IX) CMP #n Compare contents of ACC with denary number n JPE <address> Following a compare instruction, jump to <address> if the compare was True JPN <address> Following a compare instruction, jump to <address> if the compare was False JMP <address> Jump to the given address OUT Output to the screen the character whose ASCII value is stored in ACC END Return control to the operating system The current contents of the main memory, Index Register (IX) and selected values from the ASCII character set are: Address Instruction 50 LDM #0 51 STO 401 52 LDX 300 53 CMP #0 54 JPE 62 55 ADD 400 56 OUT 57 LDD 401 58 INC ACC 59 STO 401 60 INC IX 61 JMP 52 62 END … 300 2 301 5 302 0 303 4 … 400 64 401 IX 0 ASCII code table (Selected codes only) ASCII code Character 65 A 66 B 67 C 68 D 69 E

7 9608/12/M/J/19 © UCLES 2019 [Turn over Trace the program currently in memory using the following trace table. The first instruction has been completed for you. Instruction address ACC Memory address IX OUTPUT 300 301 302 303 400 401 2 5 0 4 64 0 50 0 [8]

8 9608/12/M/J/19 © UCLES 2019 (d) The ASCII character code for ‘A’ is 65 in denary. (i) Convert the denary ASCII character code for ‘A’ into 8-bit binary. [1] (ii) Convert the denary ASCII character code for ‘A’ into hexadecimal. … [1] (iii) The Unicode character code for ‘G’ is 0047 in hexadecimal. State, in hexadecimal, the Unicode character code for ‘D’. … [1]

9 9608/12/M/J/19 © UCLES 2019 [Turn over 4 Shazia is creating a computer program that will be released to the public. The program includes a video. (a) Shazia uses a microphone to record a sound track for the video. (i) Describe the internal operation of a microphone. … … … … … … [3] (ii) The script for the sound track is printed using a laser printer. Describe the internal operation of a laser printer. … … … … … … [3] (b) The video is recorded using progressive encoding. Describe progressive encoding. … … … … [2]

10 9608/12/M/J/19 © UCLES 2019 (c) Shazia’s computer has Dynamic RAM (DRAM) and Static RAM (SRAM). Explain the differences between Dynamic RAM and Static RAM. … … … … … … … … [4] (d) Shazia wants to make sure her computer program is copyrighted. (i) Define the term copyright. … … [1] (ii) Shazia does not want to release the software as open source. Explain why Shazia does not want to use an open source licence. … … … … [2] (iii) Name and describe two software licences, other than open source that Shazia could use. Licence 1 … … … Licence 2 … … … [2]

11 9608/12/M/J/19 © UCLES 2019 [Turn over 5 Moheem is creating a relational database to store data about his customers. (a) Moheem has been told a relational database addresses some of the limitations of a file-based approach by reducing data redundancy. (i) State what is meant by the term data redundancy. … … [1] (ii) Explain how a relational database can help to reduce data redundancy. … … … … … … [3] (b) Moheem uses a Database Management System (DBMS) to ensure the security and integrity of the data. (i) Explain the difference between security and integrity. … … … … [2] (ii) Name and describe two security features provided by a DBMS. Feature 1 … … … … Feature 2 … … … … [4]

12 9608/12/M/J/19 © UCLES 2019 (iii) The DBMS provides software tools for the database developer. Fill in the names of the missing software tools in the following statements. A … allows a developer to extract data from a database. A … enables a developer to create user-friendly forms and reports. [2]

13 9608/12/M/J/19 © UCLES 2019 6 (a) Draw a logic circuit to represent the logic expression: X = A OR (B AND NOT C) OR (A AND B) A B C X [5] (b) Complete the truth table for the logic expression in part (a). A B C Working space X 0 0 0 0 0 1 0 1 0 0 1 1 1 0 0 1 0 1 1 1 0 1 1 1 [4]

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16 9608/12/M/J/19 © UCLES 2019 Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the publisher will be pleased to make amends at the earliest possible opportunity. To avoid the issue of disclosure of answer-related information to candidates, all copyright acknowledgements are reproduced online in the Cambridge Assessment International Education Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download at www.cambridgeinternational.org after the live examination series. Cambridge Assessment International Education is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of the University of Cambridge Local Examinations Syndicate (UCLES), which itself is a department of the University of Cambridge. BLANK PAGE

This document consists of 11 printed pages. © UCLES 2019 [Turn over Cambridge Assessment International Education Cambridge International Advanced Subsidiary and Advanced Level COMPUTER SCIENCE 9608/12 Paper 1 Written Paper May/June 2019 MARK SCHEME Maximum Mark: 75 Published This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began, which would have considered the acceptability of alternative answers. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge International will not enter into discussions about these mark schemes. Cambridge International is publishing the mark schemes for the May/June 2019 series for most Cambridge IGCSE™, Cambridge International A and AS Level and Cambridge Pre-U components, and some Cambridge O Level components.

9608/12 Cambridge International AS/A Level – Mark Scheme PUBLISHED May/June 2019 © UCLES 2019 Page 2 of 11 Generic Marking Principles These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these marking principles. GENERIC MARKING PRINCIPLE 1: Marks must be awarded in line with: • the specific content of the mark scheme or the generic level descriptors for the question • the specific skills defined in the mark scheme or in the generic level descriptors for the question • the standard of response required by a candidate as exemplified by the standardisation scripts. GENERIC MARKING PRINCIPLE 2: Marks awarded are always whole marks (not half marks, or other fractions). GENERIC MARKING PRINCIPLE 3: Marks must be awarded positively: • marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond the scope of the syllabus and mark scheme, referring to your Team Leader as appropriate • marks are awarded when candidates clearly demonstrate what they know and can do • marks are not deducted for errors • marks are not deducted for omissions • answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the question as indicated by the mark scheme. The meaning, however, should be unambiguous. GENERIC MARKING PRINCIPLE 4: Rules must be applied consistently e.g. in situations where candidates have not followed instructions or in the application of generic level descriptors. GENERIC MARKING PRINCIPLE 5: Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may be limited according to the quality of the candidate responses seen). GENERIC MARKING PRINCIPLE 6: Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or grade descriptors in mind.

9608/12 Cambridge International AS/A Level – Mark Scheme PUBLISHED May/June 2019 © UCLES 2019 Page 3 of 11 Question Answer Marks 1(a)(i) 1 mark for any valid example e.g. 192.168.0.1 1 1(a)(ii) 1 mark for correct answer The number of IP addresses needed will exceed the number available using IPv4. 1 1(a)(iii) 1 mark per bullet point to max 2 • Too many digits per group • Too many groups of digits • The address is more than 32 bits / 4 bytes • Colons are used as separators 2 1(b)(i) 1 mark per bullet point to max 2 • The PSTN consists of many different types of communication lines • Data is transmitted in both directions at the same time // (full) duplex data transmission • The communication passes through different switching centres 2 1(b)(ii) 1 mark for benefit, 1 mark for drawback Benefit • (Probably) faster connection / communication / transmission of data • (Usually) more consistent transmission speed • Improved security Drawback • Expensive to set-up / maintain • Disruption to the dedicated line would leave no alternative 2

9608/12 Cambridge International AS/A Level – Mark Scheme PUBLISHED May/June 2019 © UCLES 2019 Page 4 of 11 Question Answer Marks 1(c) 1 mark per bullet point to max 4, max 3 for router, max 3 for gateway Only award the repeated bullet points (1 to 5 in each section) once Router: • Connects two (or more) networks • Can connect a network to a WAN // acts as the single access point for« • Receives packets and forwards towards the destination • «using the IP address of the destination • Assigns private IP addresses • Operates between similar networks // networks using the same protocol • Can be used to segment a network Gateway: • Connect two (or more) networks • Can connect a network to a WAN // acts as the single access point for« • Receives packets and send packets towards the destination • «using the IP address of the destination • Assigns private IP addresses • Connects two dissimilar networks // networks that use different protocols 4 1(d) 1 mark per bullet point to max 3 for any valid answer For example: • File server • Print server • Proxy server • Web server • Application server 3 Question Answer Marks 2(a)(i) 1 mark for correct answer • To convert a (higher level) programming language to a different form 1 2(a)(ii) 1 mark per bullet point to max 2 • Easier de-bugging • «because errors can be corrected in real time • The effect of any change made to the code can be seen immediately • Parts of the program can be tested, without all the program code being available 2 2(a)(iii) 1 mark for correct answer Assembler 1

9608/12 Cambridge International AS/A Level – Mark Scheme PUBLISHED May/June 2019 © UCLES 2019 Page 5 of 11 Question Answer Marks 2(b) 1 mark per bullet point to max 2 • The code is already written so the programmer is not starting over again which saves time • The code will have been used by many people so it should be already thoroughly tested and relatively error-free / won’t need re-testing • The programmer can use e.g. mathematical / graphics functions etc. that he may not know how to code • Use of named library functions can simplify the program and make it easier to read • The library routine code should conform to industry standards and therefore contribute towards a more robust program 2 Question Answer Marks 3(a) 1 mark for each error and correction • Line 02 should be +1 not −1 // PC ← [PC] + 1 • Line 03 should be double brackets around MAR // MDR ← [[MAR]] • Line 04 should be MDR not MAR // CIR ← [MDR] 3 3(b) 1 mark for each group to max. 2 • Data movement • Arithmetic operations • (Unconditional and conditional) jump instructions • Compare instructions • Modes of addressing 2 3(c) 1 mark per bullet • Storing 0 in 401 (line 51) • Loading memory location 300, value 2 to ACC (line 52) • Adding 64 to ACC to give 66 (line 55) • Outputting B (line 56) • Load 0 (line 57), increment ACC (line 58) and store 1 in 401 (line 59) • Incrementing IX (line 60) • Loading 5 (line 52), adding 64 (line 55), outputting E (line 56) loading 1 (line 57), incrementing ACC (line 58), storing 2 in 401 (line 59) and incrementing IX (line 60) • Load 0 (line 52) and end 8

9608/12 Cambridge International AS/A Level – Mark Scheme PUBLISHED May/June 2019 © UCLES 2019 Page 6 of 11 Instruction address ACC Memory address IX OUTPUT 300 301 302 303 400 401 2 5 0 4 64 0 50 0 51 0 [1] 52 2 [1] 53 54 55 66 [1] 56 B [1] 57 0 [1] 58 1 59 1 60 1 [1] 61 52 5 53 54 55 69 56 E [1] 57 1 58 2 59 2 60 2 61 52 0 53 [1] 54 62

9608/12 Cambridge International AS/A Level – Mark Scheme PUBLISHED May/June 2019 © UCLES 2019 Page 7 of 11 Question Answer Marks 3(d)(i) 1 mark for correct answer 0100 0001 1 3(d)(ii) 1 mark for correct answer 41 1 3(d)(iii) 1 mark for correct answer 0044 1 Question Answer Marks 4(a)(i) 1 mark per bullet point to max 3 • The microphone has a diaphragm / ribbon (accept equivalent) • The incoming sound waves cause vibrations (of the diaphragm) • «causing a coil to move past a magnet (dynamic microphone) // changing the capacitance (condenser microphone) // deforms the crystal (crystal microphone) etc. • An electrical signal is produced 3 4(a)(ii) 1 mark per bullet to max 3 • The revolving drum is initially given an electrical charge • A laser beam (bounces off moving mirrors) scans back and forth across the drum • ...discharging certain points (i.e. ‘drawing’ the letters and images to be printed as a pattern of electrical charges) • The drum is coated with oppositely charged toner (which only sticks to charged areas) • The drum rolls over electro-statically charged paper // Electro-statically charged paper is fed (towards the drum) • The ‘pattern’ on the drum is transferred to the paper • The paper is passed through the fuser to seal the image • The electrical charge is removed from the drum // the excess toner is collected 3 4(b) 1 mark per bullet to max 2 • Stores all the scan lines for an entire frame // displays / records all the frame data at the same time // not split into fields • Complete frames are displayed in sequence • The rate of picture display is the same as the frame rate. 2

9608/12 Cambridge International AS/A Level – Mark Scheme PUBLISHED May/June 2019 © UCLES 2019 Page 8 of 11 Question Answer Marks 4(c) 1 mark per bullet to max 4 • DRAM has to be refreshed / charged and SRAM does not require a refresh • DRAM uses a single transistor and capacitor and SRAM uses more than one transistor • DRAM stores each bit as a charge and in SRAM each bit is stored using a flip-flop/latch • DRAM requires higher power consumption under low levels of access, (which is significant when used in battery-powered devices because it requires more circuitry for refreshing) // SRAM uses less power (no need to refresh) • DRAM less expensive to purchase (requires fewer transistors) // SRAM is more expensive to buy (as it requires more transistors) • DRAM has slower access time/speed (because it needs to be refreshed) // SRAM has faster access times • DRAM can have higher storage/bit/data density // SRAM has lower storage/bit/data density • DRAM used in main memory and SRAM used in cache memory 4 4(d)(i) 1 mark for correct answer Formal or legal recognition of ownership of the program // Formal or legal restriction / permissions on use of the program // The intellectual property rights to the program 1 4(d)(ii) 1 mark per bullet point • She does not wish to release the source code • She does not want anyone to be able to edit / modify / share the source code/program • She wants to make money from the program 2

9608/12 Cambridge International AS/A Level – Mark Scheme PUBLISHED May/June 2019 © UCLES 2019 Page 9 of 11 Question Answer Marks 4(d)(iii) 1 mark for a name and a description of each licence to max 2 Commercial Software • The program is purchased for a fee • It restricts the number of users/possible time period for use // Limited number of installations allowed // Software key needed to install • Source code not provided // source code protected / cannot be edited • Anyone can purchase/download if agree to the terms Shareware • The program is free for a trial period // The (free) program may have limited functionality // Need to purchase / enter details after trial • Users do not have access to the source code // source code may not be edited • Users may re-distribute the software. Freeware • There is no charge for the software • The software could still be copyrighted • She can set her own restrictions on what a user can do with the program 2 Question Answer Marks 5(a)(i) 1 mark for correct answer Repeated / duplicated data 1 5(a)(ii) 1 mark per bullet point • Because each record/piece of data is stored once and is referenced by a (primary) key • Because data is stored in individual tables • «and the tables are linked by relationships • By the proper use of Primary and Foreign keys • By enforcing referential integrity • By going through the normalisation process 3 5(b)(i) 1 mark per bullet point • Security ensures that data is safe from unauthorised access // safe from loss • Integrity ensures that data is accurate / consistent / up to date 2

9608/12 Cambridge International AS/A Level – Mark Scheme PUBLISHED May/June 2019 © UCLES 2019 Page 10 of 11 Question Answer Marks 5(b)(ii) 1 mark for naming, 1 mark for description For example: • Access rights // User accounts • Restrict actions (e.g. read / read-write) of specific users // unauthorised users cannot access the database • Views • Restrict which parts of the database specific users can see • Password // Biometrics // PIN code • Prevents unauthorised access • Automatic Backup • Create regular copies of data in case of loss • Encryption • Data is incomprehensible to unauthorised users 4 5(b)(iii) 1 mark per bullet • Query Processor • Developer Interface 2 Question Answer Marks 6(a) 1 mark per gate The OR gates may be re-sequenced Alternatively: 3-input OR gate 1 mark for first three gates, and 2 marks for 3-input OR gate 5

9608/12 Cambridge International AS/A Level – Mark Scheme PUBLISHED May/June 2019 © UCLES 2019 Page 11 of 11 Question Answer Marks 6(b) 1 mark for each pair of rows (shaded) A B C Working Space X 0 0 0 0 0 0 1 0 0 1 0 1 0 1 1 0 1 0 0 1 1 0 1 1 1 1 0 1 1 1 1 1 4