Cambridge A Level Computer Science 9608 — 2015 May/June Paper 1 · Variant 1

This document consists of 16 printed pages. DC (RW/SW) 93610/2 © UCLES 2015 [Turn over Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level * 5 1 9 8 2 0 1 5 2 6 * COMPUTER SCIENCE 9608/11 Paper 1 Theory Fundamentals May/June 2015 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/15 © UCLES 2015 1 (i) Convert the following binary number into hexadecimal. 1 0 1 1 1 0 0 0 …[1] (ii) Convert the following denary number into BCD format. 9 7 …[1] (iii) Using two’s complement, show how the following denary numbers could be stored in an 8-bit register: 114 - 93 [2]

3 9608/11/M/J/15 © UCLES 2015 [Turn over 2 (a) Sound can be represented in a computer in a digital format. (i) Give the definition of the term sampling. … … …[1] (ii) Give one reason why 16-bit sampling is used in an audio compact disc (CD). … …[1] (iii) Explain what is meant by the term sampling resolution. … … … …[2] (iv) Give one benefit and one drawback of using a higher sampling resolution. Benefit … … Drawback … …[2] (b) Describe two typical features found in software for editing sound files. 1 … … 2 … …[2]

4 9608/11/M/J/15 © UCLES 2015 (c) Explain the difference between lossless and lossy data compression techniques. … … … … … …[3]

5 9608/11/M/J/15 © UCLES 2015 [Turn over 3 Five modes of addressing and five descriptions are shown below. Draw a line to connect each mode of addressing to its correct description. Mode of addressing Description direct the operand is the address of the address of the value to be used immediate the operand is the address of the value to be used indexed the operand is the offset from the current address where the value to be used is stored indirect the operand plus the contents of the index register is the address of the value to be used relative the operand is the value to be used [4]

6 9608/11/M/J/15 © UCLES 2015 4 (a) Sensors are one type of input device. For each of the following situations, name a different sensor that could be used. (i) air conditioning in an office building …[1] (ii) maintaining correct growing conditions in a greenhouse …[1] (iii) detecting an intruder in a building …[1] (b) Sensors are used to monitor seismic activity. At the end of each day, all the data are transmitted to a central computer. This is hundreds of kilometres away. Describe one way of ensuring that the integrity of the data is retained during the transmission stage. … … … … … … …[4]

7 9608/11/M/J/15 © UCLES 2015 [Turn over 5 (a) Telephone calls can be made by using: • conventional telephones (using the Public Service Telephone Network (PSTN) system) over a wired network • a computer, equipped with speakers and microphone, connected to the Internet Put a tick () in the correct column to match each description to the appropriate communication method. Description Conventional telephone using PSTN Internet-based system connection only in use whilst sound is being transmitted dedicated channel used between two points for the duration of the call connection maintained throughout the telephone call encoding schemes and compression technology used lines remain active even during a power outage [5] (b) Distinguish between the Internet and the World Wide Web (WWW). … … … … … …[3]

8 9608/11/M/J/15 © UCLES 2015 (c) Name the hardware device that is being described: (i) A device that transfers data from one network to another in an intelligent way. It has the task of forwarding data packets to their destination by the most efficient route. …[1] (ii) A device used between two dissimilar LANs. The device is required to convert data packets from one protocol to another. …[1] (iii) A device or software that provides a specific function for computers using a network. The most common examples handle printing, file storage and the delivery of web pages. …[1]

9 9608/11/M/J/15 © UCLES 2015 [Turn over 6 (a) Name the most suitable input or output device for each of the following uses. Give a different device in each case. Description of use Input or output device input of credit card number into an online form selection of an option at an airport information kiosk output of a single high-quality photograph output of several hundred high-quality leaflets input of a hard copy image into a computer [5] (b) All of the uses in part (a) involve the input or output of data. (i) Describe two methods of preventing accidental loss of data. 1 … … 2 … …[2] (ii) Describe one way of ensuring the security of the data against malicious damage. … …[1]

10 9608/11/M/J/15 © UCLES 2015 7 A system is monitored using sensors. The sensors output binary values corresponding to physical conditions, as shown in the table: Parameter Description of parameter Binary value Description of condition P oil pressure 1 pressure >= 3 bar 0 pressure < 3 bar T temperature 1 temperature >= 200°C 0 temperature < 200°C R rotation 1 rotation <= 1000 revs per minute (rpm) 0 rotation > 1000 revs per minute (rpm) The outputs of the sensors form the inputs to a logic circuit. The output from the circuit, X, is 1 if any of the following three conditions occur: either oil pressure >= 3 bar and temperature >= 200°C or oil pressure < 3 bar and rotation > 1000 rpm or temperature >= 200°C and rotation > 1000 rpm (a) Draw a logic circuit to represent the above system. P T X R [5]

11 9608/11/M/J/15 © UCLES 2015 [Turn over (b) Complete the truth table for this system. P T R Workspace 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]

12 9608/11/M/J/15 © UCLES 2015 8 (a) Explain how the width of the data bus and system clock speed affect the performance of a computer system. Width of the data bus … … … … Clock speed … … … …[3] (b) Most computers use Universal Serial Bus (USB) ports to allow the attachment of devices. Describe two benefits of using USB ports. 1 … … 2 … …[2] (c) The table shows six stages in the von Neumann fetch-execute cycle. Put the stages into the correct sequence by writing the numbers 1 to 6 in the right hand column. Description of stage Sequence number the instruction is copied from the Memory Data Register (MDR) and placed in the Current Instruction Register (CIR) the instruction is executed the instruction is decoded the address contained in the Program Counter (PC) is copied to the Memory Address Register (MAR) the value in the Program Counter (PC) is incremented so that it points to the next instruction to be fetched the instruction is copied from the memory location contained in the Memory Address Register (MAR) and is placed in the Memory Data Register (MDR) [6]

13 9608/11/M/J/15 © UCLES 2015 [Turn over Question 9 begins on page 14.

14 9608/11/M/J/15 © UCLES 2015 9 A database has been designed to store data about salespersons and the products they have sold. The following facts help to define the structure of the database: • each salesperson works in a particular shop • each salesperson has a unique first name • each shop has one or more salespersons • each product which is sold is manufactured by one company only • each salesperson can sell any of the products • the number of products that each salesperson has sold is recorded The table ShopSales was the first attempt at designing the database. FirstName Shop ProductName NoOfProducts Manufacturer Nick TX television set refrigerator digital camera 3 2 6 SKC WP HKC Sean BH hair dryer electric shaver 1 8 WG BG John TX television set mobile phone digital camera toaster 2 8 4 3 SKC ARC HKC GK (a) State why the table is not in First Normal Form (1NF). … …[1]

15 9608/11/M/J/15 © UCLES 2015 [Turn over (b) The database design is changed to: SalesPerson (FirstName, Shop) SalesProducts (FirstName, ProductName, NoOfProducts, Manufacturer) Using the data given in the first attempt table (ShopSales), show how these data are now stored in the revised table designs. Table: SalesPerson FirstName Shop Table: SalesProducts FirstName ProductName NoOfProducts Manufacturer [3]

16 9608/11/M/J/15 © UCLES 2015 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 International Examinations Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download at www.cie.org.uk after the live examination series. Cambridge International Examinations is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of University of Cambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge. (c) (i) A relationship between the two tables has been implemented. Explain how this has been done. … … … … …[2] (ii) Explain why the SalesProducts table is not in Third Normal Form (3NF). … … … …[2] (iii) Write the table definitions to give the database in 3NF. … … … …[2]

® IGCSE is the registered trademark of Cambridge International Examinations. CAMBRIDGE INTERNATIONAL EXAMINATIONS Cambridge International Advanced Subsidiary and Advanced Level MARK SCHEME for the May/June 2015 series 9608 COMPUTER SCIENCE 9608/11 Paper 1 (Written Paper), maximum raw mark 75 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 will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the May/June 2015 series for most Cambridge IGCSE®, Cambridge International A and AS Level components and some Cambridge O Level components.

Page 2 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2015 9608 11 © Cambridge International Examinations 2015 1 (i) B 8 [1] (ii) 1 0 0 1 0 1 1 1 [1] (iii) 114 0 1 1 1 0 0 1 0 – 93 1 0 1 0 0 0 1 1 [2] 2 (a) (i) Any one from: • amplitude of sound wave taken at different points in time • measurement of value of analogue signal at regular time intervals/a point in time [1] (ii) Any one from: • bit depth/sampling resolution sufficient for good quality sound • higher bit depth/sampling resolution would mean bigger files • ...hence less (music) content on each CD • can represent dynamic range of about 90 dB • 90 dB is basically the maximum dynamic range of human hearing • compromise between quality and reasonable file size [1] (iii) Any two from: • resolution is the number of distinct values available to encode/represent each sample • specified by the number of bits used to store/record each sample • sometimes referred to as bit depth • the higher the sampling resolution, the smaller the quantization error • a higher sampling resolution results in less distortion of the sound • usually 8 bit, 16 bit, 24 bit or 32 bit [2] (iv) 1 mark for benefit and 1 mark for drawback. benefit • allows for larger dynamic ranges • ...as dynamic range is approximately six times the bit depth • more accurate representation/crisper sound quality drawback • bigger files/occupies more memory/storage • longer to transmit data/download music • greater processing power needed [2]

Page 3 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2015 9608 11 © Cambridge International Examinations 2015 (b) Any two from: • edit start time, stop time and duration of any sound/timeline • extract/delete/save part of a clip • frequency, amplitude, pitch alteration • fade in/out of a clip • mix/merge multiple sound sources/tracks • combine different sources at various volume levels • pan between tracks/channels • use of filters • playback to speakers, processors or recording medium • conversion between different audio file formats • etc... [2] (c) Any three from: For full marks both techniques must be mentioned. • lossless designed to lose none of the original detail/lossless allows original file to be recreated exactly • lossless technique based on some form of replacement • mention of type of replacement, for example RLE, FLAC etc. • by example: e.g. 000–1111–222222–333 = 3–0, 4–1, 6–2, 3–3 etc. • maximum compression about 50% • lossy may result in loss of detail compared to original file/lossy does not allow original file to be re-created exactly • lossy techniques make decision about what parts of sound/sound file are important and discards other information • only keeps sounds human ear can process/discards sounds most people cannot hear • ... then applies lossless technique, for further reduction • lossy compression can reduce to about 10% • an example of jpeg, mp3 or other correct examples of compressed formats. No double credit to opposite answers, e.g. lossless maintains detail, but lossy loses detail just one mark. [3]

Page 4 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2015 9608 11 © Cambridge International Examinations 2015 3 [4] the operand is the address of the address of the value to be used the operand is the address of the value to be used the operand is the offset from the current address where the value to be used is stored the operand plus contents of index register is the address of the value to be used the operand is the value to be used direct immediate indexed indirect relative

Page 5 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2015 9608 11 © Cambridge International Examinations 2015 4 (a) answer requires a different sensor for each part, 1 mark for each part (i) temperature/thermistor [1] (ii) moisture, humidity, light/photodiode, temperature, pH [1] (iii) sound/acoustic, infrared, pressure, motion, microwave [1] (b) 1 mark for name + 3 marks for description parity check • uses even or odd parity which is decided before data sent • each byte has a parity bit • parity bit is set to 0 or 1 to make parity for byte correct • after transmission, parity of each byte re-checked • if it is different, then an error is flagged • any reference to use of parity blocks/parity byte to (identify position of incorrect bit) checksum • a calculation is carried out on the data to be sent (checksum) • the result is sent, along with data to recipient • checksum is re-calculated at receiving end • if both sums are the same, no error has occurred • if the sums are different, the data has been corrupted during transmission • request is sent to re-send data [4]

Page 6 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2015 9608 11 © Cambridge International Examinations 2015 5 (a) Description Conventional telephone using PSTN Internet-based system connection only in use whilst sound is being transmitted
dedicated channel used between two points for the duration of the call
connection maintained throughout the telephone call
encoding schemes and compression technology used
lines remain active even during a power outage
[5] (b) maximum of two marks for Internet references and maximum of two marks for world wide web references Internet • massive network of networks/interconnected network of computer devices • Internet stands for Interconnected Networks • uses TCP/IP protocol World Wide Web (www) • is a collection of (multimedia) web pages/documents • ...stored on websites • http/protocols used to transmit data • web pages are written in HTML • URLs specify the location of the web pages • web documents are accessed using browsers [3] (c) (i) router [1] (ii) gateway [1] (iii) server [1]

Page 7 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2015 9608 11 © Cambridge International Examinations 2015 6 (a) Description of use Input or output device input of credit card number into an online form Keyboard/keypad/numberpad selection of an option at an airport information kiosk touch screen output of a singe high quality photograph ink jet printer output of several hundred high quality leaflets laser printer input of a hard copy image into a computer scanner [5] (b) (i) Any two from: • frequent (or equivalent) backup EITHER to secondary media/to 3rd party server/cloud/removable devices/continuous backup OR stored remotely • disk-mirroring strategy/RAID • UPS (uninterruptable power supply)/backup generator [2] (ii) Any one from: • protection of data (or equivalent) with passwords/using password and username for logging on include e.g. fingerprint scanning • encryption • installation and use of up to date anti-malware/anti-virus • give different access rights to different users • use a firewall, • physical methods/lock doors and use secure entry devices/CCTV [1]

Page 8 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2015 9608 11 © Cambridge International Examinations 2015 7 (a) Since it is possible to simplify the original conditions, at least 3 possible answers exist for the logic circuit. Note: input T has 2 cross overs that should not be connections Note: it is possible to use a 3-input OR gate rather than the two 2-input OR gates on the top right: P T R X 1 mark 1 mark 1 mark 1 mark 1 mark X AND-gate 1 AND-gate 2 AND-gate 3 2 marks

Page 9 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2015 9608 11 © Cambridge International Examinations 2015 Alternative solution 1: Alternative solution 2: [5] Note: other solutions may be possible depending on how simplification of the original statement is done P T R X 1 mark 1 mark 1 mark 1 mark 1 mark P T R X 1 mark 1 mark 3 marks

Page 10 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2015 9608 11 © Cambridge International Examinations 2015 (b) P T R Workspace X 0 0 0 1 0 0 1 0 0 1 0 1 0 1 1 0 1 0 0 0 1 0 1 0 1 1 0 1 1 1 1 1 [4] 8 (a) maximum of 2 marks for data bus width and maximum of 2 marks for clock speed data bus width • the width of the data bus determines the number of bits that can be simultaneously transferred • increasing the width of the data bus increases the number of bits/amount of data that can be moved at one time (or equivalent) • …hence improving processing speed as fewer transfers are needed • By example: e.g. double the width of the data bus moves 2x data per clock pulse clock speed • determines the number of cycles the CPU can execute per second • increasing clock speed increases the number of operations/number of fetch-execute cycles that can be carried out per unit of time • ...however, there is a limit on clock speed because the heat generated by higher clock speeds cannot be removed fast enough [3] (b) Any two from: • devices automatically detected and configured when first attached/plug and play • it is nearly impossible to wrongly connect a device • USB has become an industrial standard • supported by many operating systems • USB 3.0 allows full duplex data transfer • later versions are backwards compatible with earlier USB systems • allows power to be drawn to charge portable devices [2] } 1 mark } 1 mark } 1 mark } 1 mark

Page 11 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2015 9608 11 © Cambridge International Examinations 2015 (c) Description of stage Sequence number the instruction is copied from the Memory Data Register (MDR) and placed in the Current Instruction Register (CIR) 3 the instruction is executed 6 the instruction is decoded 5 the address contained in the Program Counter (PC) is copied to the Memory Address Register (MAR) 1 the value in the Program Counter (PC) is incremented so that it points to the next instruction to be fetched 4 the instruction is copied from the memory location contained in the Memory Address Register (MAR) and is placed in the Memory Data Register (MDR) 2 [6]

Page 12 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2015 9608 11 © Cambridge International Examinations 2015 9 (a) Any one from: • (ShopSales) table has repeated group (of attributes) • each sales person has a number of products • FirstName, Shop would need to be repeated for each record [1] (b) One mark for SalesPerson table table: SalesPerson FirstName Shop Nick TX Sean BH John TX

Page 13 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2015 9608 11 © Cambridge International Examinations 2015 table: SalesProducts FirstName ProductName NoOfProducts Manufacturer Nick television set 3 SKC Nick refrigerator 2 WP Nick digital camera 6 HKC Sean hair dryer 1 WG Sean electric shaver 8 BG John television set 2 SKC John mobile phone 8 ARC John digital camera 4 HKC John toaster 3 GK (1 mark for FirstName column + 1 mark for remainder of table) [3]

Page 14 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2015 9608 11 © Cambridge International Examinations 2015 (c) (i) Any two from: • primary key of SalesPerson table is FirstName • links to FirstName in SalesProducts table • FirstName in SalesProductsS table is foreign key [2] (ii) • There is a non-key dependency • Manufacturer is dependent on ProductName, (which is not the primary key of the SalesProducts table) [2] (iii) SalesPerson (FirstName, Shop) –SalesProducts (FirstName, ProductName, NoOfProducts) OR SalesProducts(SalesID, FirstName, ProductName, NoOfProducts) -Product (ProductName, Manufacturer) 1 mark for correct attributes in SalesProducts and Product tables and 1 mark for correct identification of both primary keys [2]