Cambridge A Level Computer Science 9608 — 2016 Oct/Nov Paper 1 · Variant 3

This document consists of 13 printed pages and 3 blank pages. DC (KN/SG) 128900 © UCLES 2016 [Turn over Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level * 4 2 4 3 5 2 8 4 6 3 * COMPUTER SCIENCE 9608/13 Paper 1 Theory Fundamentals October/November 2016 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 9608/13/O/N/16 © UCLES 2016 1 (a) Five descriptions and seven relational database terms are shown below. Draw a line to link each description to its correct database term. Description Database term Any object, person or thing about which it is possible to store data Dataset organised in rows and columns; the columns form the structure and the rows form the content Any attribute or combination of attributes that can act as a unique key Attribute(s) in a table that link to the primary key in another table to form a relationship Attribute or combination of attributes that is used to uniquely identify a record Secondary key Candidate key Entity Foreign key Primary key Table Tuple [5] (b) Explain what is meant by referential integrity. … … … … … …[3]

3 9608/13/O/N/16 © UCLES 2016 [Turn over 2 (a) State two differences between Static RAM (SRAM) and Dynamic RAM (DRAM). 1 … … 2 … …[2] (b) (i) Explain why a computer needs an operating system. … … … …[2] (ii) Give two key management tasks carried out by an operating system. 1 … … 2 … …[2] (c) New program code is to be written in a high-level language. The use of Dynamic Link Library (DLL) files is considered in the design. Describe what is meant by a DLL file. … … … …[2]

4 9608/13/O/N/16 © UCLES 2016 3 (a) (i) Convert the denary number 46 to an 8-bit binary integer. … …[1] (ii) Convert the denary integer – 46 to an 8-bit two’s complement form. … …[1] (iii) Convert the denary number 46 into hexadecimal. … …[1] (b) Binary Coded Decimal (BCD) is another way of representing numbers. (i) Describe how denary integers larger than 9 can be converted into BCD. Give an example in your answer. … … … …[2] (ii) Describe how an 8-bit BCD representation can be converted into a denary integer. Give an example in your answer. … … … …[2]

5 9608/13/O/N/16 © UCLES 2016 [Turn over 4 Describe the basic internal operation of the following devices: (i) Keyboard … … … …[2] (ii) Optical disc … … … …[2] (iii) Optical mouse … … … …[2] (iv) Scanner … … … …[2]

6 9608/13/O/N/16 © UCLES 2016 5 A motor is controlled by a logic circuit. The circuit has inputs (0 or 1) from three sensors R, T and W. The motor is switched off when the output from the logic circuit is 1. The following table shows the three sensors and the conditions being monitored. Sensor Description Binary value Condition R rotation 0 rotation < 4000 rpm 1 rotation >= 4000 rpm T temperature 0 temperature >= 90 °C 1 temperature < 90 °C W water flow rate 0 water flow rate >= 50 litre/min 1 water flow rate < 50 litre/min The output, X, is 1 if: temperature >= 90 °C and rotation >= 4000 rpm or temperature < 90 °C and water flow rate >= 50 litre/min (i) Draw a corresponding logic circuit. R T X W [5]

7 9608/13/O/N/16 © UCLES 2016 [Turn over (ii) Give a logic statement corresponding to the logic circuit in part (i). … …[2] (iii) Complete the truth table for this system. INPUT Workspace OUTPUT X R T W 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] 6 A user watches a video available on a website. The website uses on-demand bit streaming. Describe how it is possible to watch the video without it continually pausing. … … … … … … … …[4]

8 9608/13/O/N/16 © UCLES 2016 7 A small company produces scientific magazines. The owner buys some new desktop computers. The computers are used to store thousands of colour images (diagrams and photographs). All the computers have Internet access. (a) Name three utility programs the company would use on all their computers. Describe what each program does. 1 … Description … … 2 … Description … … 3 … Description … …[6] (b) The images contained in the magazines are produced using either bitmap or vector graphics software. Give four differences between bitmap and vector graphics. 1 … … 2 … … 3 … … 4 … …[4]

9 9608/13/O/N/16 © UCLES 2016 [Turn over (c) Employees using the new computers receive training. At the end of the training, each employee completes a series of questions. Three answers given by an employee are shown below. Explain why each answer is incorrect. (i) “Encryption prevents hackers breaking into the company’s computers.” … … … …[2] (ii) “Data validation is used to make sure that data keyed in are the same as the original data supplied.” … … … …[2] (iii) “The use of passwords will always prevent unauthorised access to the data stored on the computers.” … … … …[2]

10 9608/13/O/N/16 © UCLES 2016 8 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 LDD <address> Direct addressing. Load the contents of 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. STO <address> Store contents of ACC at the given address. ADD <address> Add the contents of the given address to ACC. CMP <address> Compare contents of ACC with contents of <address> 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 diagram shows the contents of the main memory: Main memory 800 0110 0100 801 0111 1100 802 1001 0111 803 0111 0011 804 1001 0000 805 0011 1111 806 0000 1110 807 1110 1000 808 1000 1110 809 1100 0010 : : 2000 1011 0101 (a) (i) Show the contents of the Accumulator after execution of the instruction: LDD 802 Accumulator: [1]

11 9608/13/O/N/16 © UCLES 2016 [Turn over (ii) Show the contents of the Accumulator after execution of the instruction: LDX 800 Index Register: 0 0 0 0 1 0 0 1 Accumulator: Explain how you arrived at your answer. … … … …[3]

12 9608/13/O/N/16 © UCLES 2016 (b) (i) Complete the trace table below for the following assembly language program. This program contains denary values. 100 LDD 800 101 ADD 801 102 STO 802 103 LDD 803 104 CMP 802 105 JPE 107 106 JPN 110 107 STO 802 108 OUT 109 JMP 112 110 LDD 801 111 OUT 112 END : : 800 40 801 50 802 0 803 90 Selected values from the ASCII character set: ASCII code 40 50 80 90 100 Character ( 2 P Z d Trace table: ACC Memory address OUTPUT 800 801 802 803 40 50 0 90 [4]

13 9608/13/O/N/16 © UCLES 2016 (ii) There is a redundant instruction in the code in part (b)(i). State the address of this instruction. …[1] (c) The program used the ASCII coding system for character codes. An alternative coding system is Unicode. (i) Give two disadvantages of using ASCII code. 1 … … 2 … …[2] (ii) Describe how Unicode is designed to overcome the disadvantages of ASCII. … … … …[2]

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16 9608/13/O/N/16 © UCLES 2016 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. BLANK PAGE

® IGCSE is the registered trademark of Cambridge International Examinations. This document consists of 10 printed pages. © UCLES 2016 [Turn over Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level COMPUTER SCIENCE 9608/13 Paper 1 Written Paper October/November 2016 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 will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the October/November 2016 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 – October/November 2016 9608 13 © UCLES 2016 1 (a) One mark for each correct line. Two lines from any box on left means no mark for that description. Description Database term [5] Any object, person or thing about which it is possible to store data Dataset organised in rows and columns; the columns form the structure and the rows form the content Any attribute or combination of attributes that can qualify as a unique key Attribute(s) in a table that link to a primary key in another table to form a relationship Attribute or combination of attributes that is used to uniquely identify a record Secondary key Candidate key Entity Foreign key Primary key Table Tuple

Page 3 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2016 9608 13 © UCLES 2016 (b) Any three from: • Ensures related data in tables are consistent • If one table has a foreign key (the ‘foreign’ table)… • … then it is not possible to add a record to that table / the ‘foreign’ table • … unless there is a corresponding record in the linked table with a corresponding primary key (the ‘primary’ table) • Cascading delete • If a record is deleted in the ‘primary’ table… • all corresponding linked records in ‘foreign’ tables must also be deleted • Cascading update • If a record in the ‘primary’ table is modified… • … all linked records in foreign tables will also be modified [3] 2 (a) Any two from: • DRAM has to be refreshed / charged // SRAM does not request a refresh • DRAM uses a single transistor and capacitor // SRAM uses more than one transistor to form a memory cell // SRAM has more complex circuitry • DRAM stores each bit as a charge // SRAM each bit is stored using a flip-flop / latch • DRAM uses higher power( 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 // SRAM used in cache memory [2]

Page 4 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2016 9608 13 © UCLES 2016 (b) (i) Any two from • The hardware is unusable without an OS // hides complexity of hardware from user • Acts as an interface / controls communications between user and hardware / hardware and software • Provides software platform / environment on which other programs can be run [2] (ii) Any two from: • Process / task / resource management • Main memory management • Peripheral / hardware / device management • File / secondary storage management • Security management • Provision of a software platform / environment on which other programs can be run – only if not given in part (b)(i) • Interrupt handling • Provision of a user interface run – only if not given in part (b)(i) [2] (c) Any two from: • A DLL file is a shared library file • Code is saved separately from the main .EXE files • Code is only loaded into main memory when required at run-time • The DDL file can be made available to several applications (at the same time) [2]

Page 5 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2016 9608 13 © UCLES 2016 3 (a) (i) 0 0 1 0 1 1 1 0 [1] (ii) 1 1 0 1 0 0 1 0 [1] (iii) 2 E [1] (b) (i) One mark for the explanation and one mark for the example • Each denary digit is written as a 4-bit binary number • Example: 46 = 0100 0110 [2] (ii) One mark for the explanation and one mark for the example • Binary number is split up into groups of 4 bits (starting from the right) // Each group of 4 bits is converted to a denary digit • Example: 0011 0111 = 37 [2] 4 (i) Keyboard Any two from: • Uses switches and circuits to translate keystrokes into signals the computer can understand • The key matrix is a grid of circuits / three layers of plastic underneath the keys • Each circuit is broken beneath the key / middle layer contains holes • When key pressed, a circuit is made / completed and a signal is sent • Processor compares location of signal from key matrix to a character map stored on ROM • A character code for each key press is saved in a keyboard buffer [2] (ii) Optical Disc Any two from: • Drive motor is used to spin the disc • Tracking mechanism moves the laser assembly • A lens focuses the laser onto the disc • Laser beam is shone onto disc to read / write • Surface of disc has a reflective metal layer / phase change metal alloy • Track(s) on the disc have sequence of pits and lands / amorphous and crystalline state • Reflected light in then encoded as a bit pattern [2]

Page 6 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2016 9608 13 © UCLES 2016 (iii) Optical mouse Any two from: • Laser / light shines onto a surface • Through a (polished) ring at the base • The light is reflected from the surface through the ring • Sensor detects reflected light • Capturing details / photograph of surface (under the ring) • At about 1500 times per second • As the mouse moves the sensor detects changes in the surface detail / photograph • Which are translated into movement (change of x and y co-ordinates) • The processor/software updates the position of the cursor on the screen [2] (iv) Scanner Any two from: • Main component of a scanner is a CCD array • CCD is a collection of light sensitive diodes • Laser beam / light is shone onto the source document/barcode • The scanned image reaches the CCD through mirrors and lenses • Sensors detect levels of reflected light • Brighter light results in greater electrical charge • Light intensity is converted (by software) to a digital value [2]

Page 7 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2016 9608 13 © UCLES 2016 5 (a) (i) One mark for each correct gate. [5] (ii) ( ) ( ) . . RT T W + // (R AND NOT T) OR (T AND NOT W) [2] (iii) One mark for each pair of lines as shaded. INPUT Working space OUTPUT X R T W 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 0 [4] R T W X

Page 8 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2016 9608 13 © UCLES 2016 6 Any four from: • User needs high-speed broadband (connection) • Data is streamed to a buffer (in the computer) • Buffering stops video pausing as bits streamed • As buffer is emptied, it fills up again so that viewing is continuous • Actual playback is (a few seconds) behind the time the data is received by computer [4] 7 (a) One mark for the name and one mark for the explanation for three utility programs • Disk formatter • Prepares a hard disk to allow data to be stored on it • Virus checker • Checks for viruses and then quarantines removes any virus found • File compression • Reduces file size by removing redundant details (lossy / lossless) • Backup software • Makes copy of files on another medium in case of corruption / loss of data • Firewall • Prevents unauthorised access to computer system from external sources [6] (b) Four from: • Bitmap is made up of pixels // Vector graphic store a set of instructions about how to draw the shape • Bitmap files are usually bigger than vector graphics files // Take up more memory space • Enlarging a bitmap can mean the image is pixelated // vector graphic can be enlarged without the image becoming pixelated • Bitmap images can be compressed (with significant reduction in file size) // Vector graphic images do not compress well • Bitmaps are suitable for photographs / scanned images // Vector graphics are suitable for more geometric shapes • Bitmap graphics use less processing power than vector graphics • Individual elements of a bitmap cannot be grouped // Individual elements of a vector graphic can be grouped • Vector graphics need to be ‘rasterised’ in order to display or print [4]

Page 9 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2016 9608 13 © UCLES 2016 (c) (i) • Hackers can still access the data (and corrupt it, change it or delete it) • Encryption simply makes data incomprehensible (without decryption key / algorithm) [2] (ii) Any two from: • This is an explanation of data verification (not validation) • Data validation ensures that data is reasonable / sensible / within a given criteria • Original data may have been entered correctly but is not reasonable (e.g. age of 210) [2] (iii) • A password does not prevent unauthorised access, it makes it more difficult • Password can be guessed (if weak) // Password can be stolen // A relevant example of misappropriation of password [2] 8 (a) (i) Accumulator: 1 0 0 1 0 1 1 1 [1] (ii) One mark for answer and two marks for explanation Accumulator: 1 1 0 0 0 0 1 0 • Index Register contains 1001 = 9 • 800 + 9 = 809 [3] (b) (i) ONE mark for each correct row. ACC Memory address OUTPUT 800 801 802 803 40 50 0 90 40 90 90 90 90 Z [4] (ii) 107 [1]

Page 10 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2016 9608 13 © UCLES 2016 (c) (i) Any two from: • Only 128 / 256 characters can be represented • Uses values 0 to 127 (or 255 if extended form) / one byte • Many characters used in other languages cannot be represented • In extended ASCII the characters from 128 to 255 may be coded differently in different systems [2] (ii) Any two from: • Uses 16, 24 or 32 bits / two, three or four bytes • Unicode is designed to be a superset of ASCII • Designed so that most characters (in other languages) can be represented [2]