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

This document consists of 13 printed pages and 3 blank pages. DC (SC) 163548/3 © UCLES 2019 [Turn over Cambridge Assessment International Education Cambridge International Advanced Subsidiary and Advanced Level * 1 0 3 1 1 0 2 9 2 8 * COMPUTER SCIENCE 9608/11 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 9608/11/M/J/19 © UCLES 2019 1 Devices connected to the Internet have IP (Internet Protocol) addresses. (a) Three IPv4 addresses are given. Circle either Valid or Invalid to indicate whether each address is valid or invalid. Explain your decision. Address 1: 3A.21.2H.1 Valid / Invalid Explanation … … Address 2: 299.53.2.2 Valid / Invalid Explanation … … Address 3: 192.2.1.0 Valid / Invalid Explanation … … [3] (b) A website can be accessed using either the Uniform Resource Locator (URL) or the IP address. Describe how a URL is converted into its matching IP address. … … … … … … [3] (c) People use the Internet to stream media. Complete the following statements by filling in the names of the missing methods of bit streaming. … bit streaming is used when watching a live stream of events that are currently taking place. The event is captured live with a video camera connected to a computer, and it cannot be paused or rewound. … bit streaming is used when watching an event that has taken place in the past. Existing media are encoded to bit streaming format and uploaded to a server. It can be paused and rewound. [2]

3 9608/11/M/J/19 © UCLES 2019 [Turn over (d) A recording of a concert is stored as a file. The file is compressed using lossy compression before it is streamed to users. (i) State why this file needs to be compressed. … … [1] (ii) Define the term lossy compression. … … [1] (iii) The file could be compressed using lossless compression. Explain why lossy compression is a more appropriate compression technique than lossless for this file. … … … … … … [3]

4 9608/11/M/J/19 © UCLES 2019 2 A software company produces software and distributes it under different software licences. (a) Four descriptions of software licences are given. Write the type of software licence that best fits each description. Use a different type of licence for each description. 1. The software can be legally used, only after a fee has been paid. Licence type … 2. The source code comes with the software. If the software is modified, the edited source code must be released under the same conditions as the original software. Licence type … 3. The software is free for a trial period and then a fee is requested, or expected, if the user wants to continue to use the software. Licence type … 4. The source code comes with the software. The software is free to be downloaded, edited, and distributed, possibly without restriction. Licence type … [4] (b) The software company stores information about customers and the software licences they have purchased. The company considers a file-based approach for the storage and retrieval of data. (i) Give three limitations of a file-based approach to store the data. 1 … … 2 … … 3 … … [3]

5 9608/11/M/J/19 © UCLES 2019 [Turn over (ii) The software company decides to use a database to overcome the limitations of a file-based system. Some of these limitations are addressed through the logical schema. Name and describe two levels of the schema of a database. Name 1 … Description … … Name 2 … Description … … [4]

6 9608/11/M/J/19 © UCLES 2019 (c) The database has the following tables: CUSTOMER(CustomerID, CompanyName) SOFTWARE(SoftwareID, SoftwareName, OperatingSystem, Description) LICENCE( LicenceID, CustomerID, SoftwareID, DateOfPurchase, LicenceType, Cost, ExpiryDate) (i) Identify the type of relationship that exists between the tables CUSTOMER and LICENCE. … … [1] (ii) Describe how the relationship is created between the tables CUSTOMER and LICENCE. … … … … [2] (iii) The company needs a list of all software licences that have an expiry date on or before 31/12/2019. Write an SQL query to return the fields CustomerID, SoftwareID, LicenceType, Cost and ExpiryDate for all licences that expire on, or before 31/12/2019. Group the output by CustomerID, and in ascending order of cost. … … … … … … … … … [5]

7 9608/11/M/J/19 © UCLES 2019 [Turn over 3 Kimmy has written a program in a high-level language. (a) Kimmy has used library routines in the program. (i) Describe two advantages of using library routines in the program. 1 … … … … 2 … … … … [4] (ii) Describe what is meant by a Dynamic Link Library (DLL). … … … … [2] (b) Three translators are compilers, interpreters, and assemblers. (i) State one benefit of Kimmy using an interpreter during the development of the program. … … [1] (ii) State three benefits of Kimmy using a compiler when the program is complete. 1 … … 2 … … 3 … … [3]

8 9608/11/M/J/19 © UCLES 2019 4 A software developer works in a team for a large software development company. (a) Two principles of the ACM/IEEE Software Engineering Code of Ethics are: • developers must act consistently with the public interest • developers must act in the best interest of their client and employer. Name and describe three other principles in the ACM/IEEE Software Engineering Code of Ethics. Principle 1 … Description … … … Principle 2 … Description … … … Principle 3 … Description … … … [6] (b) The software development company uses data backup and disk-mirroring to keep their data secure. Explain how data backup and disk-mirroring allow the company to recover from data loss. Data backup … … … … Disk-mirroring … … … … [4]

9 9608/11/M/J/19 © UCLES 2019 [Turn over 5 A simple program written in assembly language is translated using a two-pass assembler. (a) The table contains some of the tasks performed by a two-pass assembler. Tick (✓) one box in each row to indicate whether the task is performed at the first or second pass. The first row has been completed for you. Task First pass Second pass Creation of symbol table ✓ Expansion of macros Generation of object code Removal of comments [2] (b) The processor’s instruction set can be grouped according to their function. For example, one group is modes of addressing. Identify two other groups of instructions. 1 … … 2 … … [2]

10 9608/11/M/J/19 © UCLES 2019 (c) The 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 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 20 LDM #0 21 STO 300 22 CMP #0 23 JPE 28 24 LDX 100 25 ADD 301 26 OUT 27 JMP 30 28 LDX 100 29 OUT 30 LDD 300 31 INC ACC 32 STO 300 33 INC IX 34 CMP #2 35 JPN 22 36 END … 100 65 101 67 102 69 103 69 104 68 … 300 301 33 IX 0 ASCII code table (Selected codes only) ASCII Code Character 65 A 66 B 67 C 68 D 69 E 97 a 98 b 99 c 100 d 101 e

11 9608/11/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 100 101 102 103 104 300 301 65 67 69 69 68 33 0 20 0 [8]

12 9608/11/M/J/19 © UCLES 2019 6 A student records a video using a digital camera. (a) The recording uses interlaced encoding. Describe interlaced encoding. … … … … … … … [3] (b) State one benefit of using interlaced encoding compared to progressive encoding. … … [1] (c) A video can be compressed using spatial redundancy or temporal redundancy. Explain how temporal redundancy compresses a video. … … … … … [2] (d) A sound track is recorded for the video. (i) Describe how a computer encodes the sound track. … … … … … … [3]

13 9608/11/M/J/19 © UCLES 2019 (ii) Explain how the sampling rate and sampling resolution affect the file size of the sound track. Sampling rate … … Sampling resolution … … [2]

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16 9608/11/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 9 printed pages. © UCLES 2019 [Turn over Cambridge Assessment International Education Cambridge International Advanced Subsidiary and Advanced Level COMPUTER SCIENCE 9608/11 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.

9608/11 Cambridge International AS/A Level – Mark Scheme PUBLISHED May/June 2019 © UCLES 2019 Page 2 of 9 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.

9608/11 Cambridge International AS/A Level – Mark Scheme PUBLISHED May/June 2019 © UCLES 2019 Page 3 of 9 Question Answer Marks 1(a) 1 mark for each correct indication and explanation 3A.21.2H.1 Invalid H is not a valid hexadecimal digit 299.53.2.2 Invalid 299 is not in the correct range 192.2.1.0 Valid Consists of four numbers in the range 0–255 separated by full stops 3 1(b) 1 mark per bullet point to max 3 • URL is parsed to obtain the Domain name • Domain name is sent to the nearest Domain Name Server (DNS) • DNS holds a list of Domain names and matching IP addresses • DNS name resolver searches its database for the Domain name • If DNS does not find the Domain name, the request is forwarded to a higher level DNS • If the Domain name is found, the IP address is returned • If the Domain name is not found, the request is passed to a higher level server • If the Domain name is finally not found, an error message is generated 3 1(c) 1 mark for each correct term Real-time On-demand 2 1(d)(i) 1 mark per bullet point to max 1 • The data files are very large • It would take a long time to send the uncompressed file // Compressed files will download faster • A higher bandwidth would be needed to transmit the uncompressed file 1 1(d)(ii) 1 mark per bullet point to max 1 • Data is lost • The decompressed file is not the same as the original 1 1(d)(iii) 1 mark per bullet point to max 3 • Lossy creates a smaller file than lossless // lossy compresses further than lossless • The recording of the concert is a large file size and needs significant reduction in size • Lossy removes detail which can be lost without people noticing • By example e.g. reduction in sound quality will not be noticed 3

9608/11 Cambridge International AS/A Level – Mark Scheme PUBLISHED May/June 2019 © UCLES 2019 Page 4 of 9 Question Answer Marks 2(a) 1 mark for each correct term • Commercial Licence • Free Software Licence • Shareware Licence • Open Source Licence 4 2(b)(i) 1 mark per bullet point to max 3 • Data redundancy // data is repeated in more than one file • Data dependency // changes to data means changes to programs accessing that data • Lack of data integrity // entries that should be the same can be different in different places • Lack of data privacy // all users have access to all data if a single flat file 3 2(b)(ii) 1 mark for each correct name, 1 mark for each matching description, max 2 marks per level • External • The individual’s view(s) of the database • Conceptual • Describes the data as seen by the applications making use of the DBMS • Describes the ‘views’ which users of the database might have • Physical / Internal • Describes how the data will be stored on the physical media • Logical • Describes how the relationships will be implemented in the logical structure of the database 4 2(c)(i) 1-to-many // 1 customer to/has many licences 1 2(c)(ii) 1 mark per bullet point • CustomerID is the Primary key in CUSTOMER table • Links to CustomerID as a Foreign key in LICENCE table 2

9608/11 Cambridge International AS/A Level – Mark Scheme PUBLISHED May/June 2019 © UCLES 2019 Page 5 of 9 Question Answer Marks 2(c)(iii) 1 mark per bullet point • Select with correct 5 fields • From LICENCE • Where ExpiryDate <= '31/12/2019' (any appropriate date type) • Group by CustomerID • Order by Cost (with or without ASC, but not DESC) SELECT CustomerID, SoftwareID, LicenceType, Cost, ExpiryDate FROM LICENCE WHERE ExpiryDate <= '31/12/2019' GROUP BY CustomerID ORDER BY Cost; 5 Question Answer Marks 3(a)(i) 1 mark for each advantage, 1 mark for a valid expansion to max 2 × 2 • Code is already tested • «so it is more robust/likely to work • Saves programming time • «code does not have to be written/re-written from scratch • The programmer can use e.g. mathematical functions • «that s/he may not know how to code • If there is an improvement in the library routine • «the program updates automatically 4 3(a)(ii) 1 mark per bullet point to max 2 • A collection of self-contained (shared library) programs • «that are already compiled • Linked to the main program during execution • Library program code is separate from the .EXE file • Library file only loaded into memory when required at run time • A DLL file can be made available to several applications (at the same time) • If DLL routine is updated the program that uses it will run the update 2 3(b)(i) 1 mark per bullet point to max 1 • Errors can be corrected as they occur • Can run a partially complete program when developing • The effect of any change made to the code can be seen immediately 1

9608/11 Cambridge International AS/A Level – Mark Scheme PUBLISHED May/June 2019 © UCLES 2019 Page 6 of 9 Question Answer Marks 3(b)(ii) 1 mark per bullet point to max 3 • Produces an executable file • User does not have access to source code • It will (probably) be faster to run the executable • Code does not have to be compiled each time it is run • Does not need the compiler to be present at run-time 3 Question Answer Marks 4(a) 1 mark for naming a principle, 1 mark for description to max 3 × 2 • Product • Software engineers shall ensure that their products and related modifications meet the highest professional standards possible. • Judgement • Software engineers shall maintain integrity and independence in their professional judgement. • Management • Software engineering managers and leaders shall subscribe to and promote an ethical approach to the management of software development and maintenance. • Profession • Software engineers shall advance the integrity and reputation of the profession consistent with the public interest. • Colleagues • Software engineers shall be fair to and supportive of their colleagues. • Self • Software engineers shall participate in life-long learning regarding the practice of their profession and shall promote an ethical approach to the practice of the profession. 6 4(b) 1 mark per bullet point to max 2 × 2 Data backup • A copy of data will have been made and stored elsewhere. • If the original is lost, the backup can be used to restore the data. Disk-mirroring • The data is stored on two disks simultaneously. • If the first disk drive fails, the data is accessed from the second disk. 4

9608/11 Cambridge International AS/A Level – Mark Scheme PUBLISHED May/June 2019 © UCLES 2019 Page 7 of 9 Question Answer Marks 5(a) 1 mark for two correct ticks, 2 marks for three correct ticks Task First pass Second pass Creation of symbol table ✓ Expansion of macros ✓ Generation of object code ✓ Removal of comments ✓ 2 5(b) 1 mark per bullet point to max 2 • Data movement • Input and output of data • Arithmetic operations • Jump instructions • Compare instructions 2 5(c) 1 mark per bullet point • Storing 0 in 300 (line 21) • Loading 65 (line 28) • Outputting A (line 29) • Loading 0 (line 30), incrementing ACC (line 31) and storing in 300 (line 32) • Incrementing IX (line 33) • Loading 67 (line 24) and adding 33 (line (25) • Outputting d (line 26) • Loading 1 (line 30), incrementing ACC (line 31), storing in 300 (line 32) and incrementing IX (line 33) 8

9608/11 Cambridge International AS/A Level – Mark Scheme PUBLISHED May/June 2019 © UCLES 2019 Page 8 of 9 Instruction address ACC Memory address IX OUTPUT 100 101 102 103 104 300 301 65 67 69 69 68 33 0 20 0 21 0 22 23 28 65 29 A 30 0 31 1 32 1 33 1 34 35 22 24 67 25 100 26 d 27 30 1 31 2 32 2 33 2 34 36

9608/11 Cambridge International AS/A Level – Mark Scheme PUBLISHED May/June 2019 © UCLES 2019 Page 9 of 9 Question Answer Marks 6(a) 1 mark per bullet point to max 3 • The data from a single frame is split into two separate fields • One field has data for the odd numbered rows/lines and the other field has data for the even numbered rows/lines • Odd numbered line fields alternate with even numbered line fields • The viewer sees data from two frames simultaneously 3 6(b) 1 mark per bullet point to max 1 • Produces what appears to be a higher refresh rate • Lower bandwidth needed // Halves the bandwidth requirements 1 6(c) 1 mark per bullet point to max 2 • Identifies pixels that do not change between frames • Records only the differences between the frames 2 6(d)(i) 1 mark per bullet point to max 3 • The amplitude of the wave is measured /sound wave is sampled • At set/regular time intervals • Each sample is stored as a binary number • Samples are stored in order in a file 3 6(d)(ii) 1 mark per bullet point to max 1 for each Sample rate: • Increasing the sample rate means more samples per second hence more bits per second and larger file size • Decreasing the sample rate means fewer samples per second hence fewer bits per second and smaller file size Sample resolution: • A higher sampling resolution means more bits per sample and a larger file size • A lower sampling resolution means fewer bits per sample. a smaller file size 2