Cambridge A Level Computer Science 9608 — 2021 Oct/Nov Paper 1 · Variant 2

This document has 16 pages. Any blank pages are indicated. Cambridge International AS & A Level DC (PQ) 205100/3 © UCLES 2021 [Turn over * 2 0 8 0 1 2 7 1 9 5 * COMPUTER SCIENCE 9608/12 Paper 1 Theory Fundamentals October/November 2021 1 hour 30 minutes You must answer on the question paper. No additional materials are needed. INSTRUCTIONS ● Answer all questions. ● Use a black or dark blue pen. ● Write your name, centre number and candidate number in the boxes at the top of the page. ● Write your answer to each question in the space provided. ● Do not use an erasable pen or correction fluid. ● Do not write on any bar codes. ● You may use an HB pencil for any diagrams, graphs or rough working. ● Calculators must not be used in this paper. INFORMATION ● The total mark for this paper is 75. ● The number of marks for each question or part question is shown in brackets [ ]. ● No marks will be awarded for using brand names of software packages or hardware.

2 9608/12/O/N/21 © UCLES 2021 1 A computer has Random Access Memory (RAM) and Read Only Memory (ROM). Tick (✓) one or more boxes in each row to identify whether each statement refers to RAM, ROM or both. Statement RAM ROM Stores data permanently It is volatile Stores the start-up instructions for the computer Directly accessed by the CPU Type of main memory Stores currently running applications Can be static or dynamic [3] 2 A travel company is designing a website. (a) The bitmap logo for the travel company is shown. Each colour is represented by a letter, for example, R = red, B = black, W = white. Bitmap Logo R R R R R R R R R B B B B B W R R B W W W B W R R B W W W W W R R B W W B B W R R B W W W B W R R B B B B B W R R R R R R R R R (i) State the minimum number of bits needed to represent each pixel in the bitmap logo. … [1]

3 9608/12/O/N/21 © UCLES 2021 [Turn over (ii) Calculate the minimum file size, in bytes, of the bitmap logo. Show your working. Working … … … … File size … [3] (b) The travel company uploads a video to its website. The video is stored as an MP4 file. MP4 is an example of a multimedia container format. Describe what is meant by a multimedia container format. … … … … [2] (c) Complete the following sentences that describe two terms related to videos. … is when a sequence of consecutive pixels in the same frame have the same value. … is when a pixel in the same location in two consecutive frames has the same value. [2]

4 9608/12/O/N/21 © UCLES 2021 3 Upali travels for his work and uses his mobile phone to access the World Wide Web (WWW) and to communicate with his office by email. His office has a fixed connection to the Internet. (a) Identify two types of communication systems that support the transmission of his data. 1 … … 2 … … [2] (b) Upali connects his computer to the Local Area Network (LAN) when he is in the office. The network uses both copper cables and fibre optic cables. Identify two other examples of network hardware that can be used in a LAN. 1 … … 2 … … [2] (c) Checksum is one method used for verification of transmitted data within a network. Name and describe one other method of verifying transmitted data. Method … Description … … … … … [3]

5 9608/12/O/N/21 © UCLES 2021 [Turn over (d) Upali works for a company that stores data on a web server. Describe two security measures that can be used to protect a web server from unauthorised access. 1 … … … … 2 … … … … [4]

6 9608/12/O/N/21 © UCLES 2021 4 The following table shows part of the instruction set for a processor. The processor 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 location at the given address to ACC CMP <address> Compare the contents of ACC with the contents of <address> SUB <address> Subtract the contents of the given address from the ACC INC <register> Add 1 to the contents of the register (ACC or IX) DEC <register> Subtract 1 from the contents of the register (ACC or IX) STO <address> Store contents of ACC at the given address END Return control to the operating system (a) The instructions in the processor’s instruction set can be grouped according to their function. (i) Identify three different instruction groups from the instructions given in the table. 1 … 2 … 3 … [3] (ii) Identify one instruction group not given in the table. … [1]

7 9608/12/O/N/21 © UCLES 2021 [Turn over (b) The following are four special purpose registers used in the processor: • Program Counter (PC) • Memory Data Register (MDR) • Memory Address Register (MAR) • Current Instruction Register (CIR) Describe the purpose of any three registers from the four given. Register 1 … Description … … … Register 2 … Description … … … Register 3 … Description … … … [6]

8 9608/12/O/N/21 © UCLES 2021 5 Jackie is writing a program in a high-level language (HLL). The program makes use of Dynamic Link Library (DLL) files. (a) Complete the following sentences about DLL files by writing the missing words from the list given below. closed corrupted directory edited errors executable opened recompile running tested validated verified The … file does not contain the library routines. A DLL file can be … without having to … the calling program. One drawback of a DLL file is that the main program could stop working if the DLL file is … . [4] (b) Jackie will use language translation software to run her HLL program. Identify and describe one type of language translator. Translator … Description … … … … … … … [4] (c) Explain the reasons why Jackie should copyright her program. … … … … [2]

9 9608/12/O/N/21 © UCLES 2021 [Turn over 6 A computer has file compression and defragmenter software. Describe these utility programs. File compression … … … … Defragmenter … … … … [4] 7 Complete the truth table for the logic expression: X = NOT(A AND B) OR NOT((C OR A) AND (B OR C)) 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]

10 9608/12/O/N/21 © UCLES 2021 8 An employment agency keeps records of its contracts with employers and workers in a relational database. These are some of the tables in the database: EMPLOYER(EmpId, EmpName, EmpAddress, EmpPhoneNumber) WORKER(WkId, WkFirstName, WkLastName, WkAddress, WkPhoneNumber) CONTRACT_TYPE(ConTypeId, ConName) CONTRACT(ConId, ConTypeId, EmpId, WkId, RefConNumber) (a) Complete the entity-relationship (E-R) diagram for this part of the database. EMPLOYER WORKER CONTRACT CONTRACT_TYPE [3] (b) Write a Data Definition Language (DDL) statement to change the CONTRACT table to remove the attribute RefConNumber. … … … … [2]

11 9608/12/O/N/21 © UCLES 2021 [Turn over (c) The following table has examples of DDL and Data Manipulation Language (DML) statements. Tick (✓) one box in each row to identify whether each statement is an example of DML or DDL. Statement DML DDL ADD PRIMARY KEY ALTER TABLE SELECT FROM INNER JOIN CREATE DATABASE [2] (d) The field WkPhoneNumber cannot be empty and must have a maximum of 14 characters. Describe two ways the field WkPhoneNumber can be validated. 1 … … … … 2 … … … … [4] (e) State what is meant by a candidate key. … … [1] (f) Describe what is meant by a secondary key. … … … … [2]

12 9608/12/O/N/21 © UCLES 2021 (g) The database is stored on a magnetic hard disk. Describe the basic internal layout and operation of a magnetic hard disk drive. … … … … … … … … … … [5] 9 The sequence of operations shows, in register transfer notation, the fetch stage of the fetch-execute cycle. 1 MAR ← [PC] 2 PC ← [PC] + 1 3 MDR ← [[MAR]] 4 CIR ← [MDR] Write a description of each of the three register transfer notations given in the following table. Register transfer notation Description MAR ← [PC] … … PC ← [PC] + 1 … … MDR ← [[MAR]] … … [3]

13 9608/12/O/N/21 © UCLES 2021 10 An 8-bit binary number can be interpreted in many ways. (a) State the number of different values that an 8-bit unsigned binary integer can represent. … [1] (b) Give the smallest and largest denary values that an 8-bit two’s complement integer can represent. Smallest … Largest … [2]

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16 9608/12/O/N/21 © UCLES 2021 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 2021 [Turn over Cambridge International AS & A Level COMPUTER SCIENCE 9608/12 Paper 1 Theory Fundamentals October/November 2021 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 October/November 2021 series for most Cambridge IGCSE™, Cambridge International A and AS Level components and some Cambridge O Level components.

9608/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2021 © UCLES 2021 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.

9608/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2021 © UCLES 2021 Page 3 of 9 Question Answer Marks 1 1 mark for each shaded set of rows Statement RAM ROM Stores data permanently  It is volatile  Stores the start-up instructions for the computer  Directly accessed by the CPU   Type of main memory   Stores currently running applications  Can be static or dynamic  3 Question Answer Marks 2(a)(i) 2 bits 1 2(a)(ii) 2 marks for correct working, 1 mark for correct answer Working: • Pixels is 8 * 8 • Bytes = (2 * 8 * 8) / 8 // (2 * 64) / 8 Answer: 16 (bytes) 3 2(b) 1 mark per bullet point to max 2 • A metafile / wrapper • …that contains audio and video // …that contains various different types of data • Describes how the (encoded) data is stored • Is not confined to any one codec / compression method • Synchronises the different types of data (on playback) 2 2(c) 1 mark for each correct term • Spatial redundancy is when a sequence of consecutive pixels in the same frame have the same value. • Temporal redundancy is when a pixel in the same location in two consecutive frames has the same value. 2

9608/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2021 © UCLES 2021 Page 4 of 9 Question Answer Marks 3(a) 1 mark per bullet point to max 2 • Cell phone network • Satellite system • Public Switched Telephone Network 2 3(b) 1 mark per bullet point to max 2 Many correct answers, for example: • Server • Router • Gateway • Radio transmitter/receiver //WAP • Hub • Switch • Repeater 2 3(c) 1 mark for name and max 2 marks for matching description Parity check • Counts if the number of 1s or 0s in each byte is odd or even • Adds a bit to make the number odd or even • Parity is re-calculated at receiving end and a change in parity indicates corruption Echo check • Receiver sends data back to sender • Sender compares data received with original • Sender either confirms or resends data Automatic repeat request (ARQ) • Uses error detection method to detect errors in individual packets • Sends a negative acknowledgement if an error • Uses timeouts to detect missing packets • Automatically asks for a repeat of the data from the sender 3

9608/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2021 © UCLES 2021 Page 5 of 9 Question Answer Marks 3(d) 1 mark per bullet point to max 2 per security measure, max 4 in total e.g. • Firewall • …denies access to data that does not conform to set rules • ... maintains a blacklist/whitelist of IP addresses • Proxy • …denies access to data that does not conform to set rules • … prevents some requests ever reaching the server • Authentication • ... makes use of usernames and strong passwords... • ... without a correct unique combination of characters data on the server cannot be accessed • ... makes use of biometrics ... • ... unique features of individuals that cannot be guessed • ... makes use of two step verification ... • ... a verification code is sent to a mobile phone or other device 4 Question Answer Marks 4(a)(i) 1 mark per bullet point to max 2 • Compare instructions • Arithmetic operations • Data movement 3 4(a)(ii) 1 mark only from • Unconditional and conditional jump instructions • Input and output of data 1 4(b) 1 mark per bullet point to max 2 per register, max 6 in total Program Counter • Points to the address ... • ... of the next instruction to be fetched • So the address can be transferred to/from the MAR Memory Address Register • Points to the address where data to be fetched/stored is located • So data can be transferred to/from the MDR Memory Data Register • Holds the data received from/ transmitted to memory • So data can be received from/transmitted to the CIR Current Instruction Register • Holds the data received from the MDR • CIR stores the current instruction being processed 6

9608/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2021 © UCLES 2021 Page 6 of 9 Question Answer Marks 5(a) 1 mark per correct word The executable file does not contain the library routines. A DLL file can be edited without having to recompile the calling program. One drawback of a DLL file is that the main program could stop working if the DLL file is corrupted. 4 5(b) 1 mark for name, 1 mark per bullet point to max 3 for description Interpreter • Converts high level language code into low level code • Translates and runs one line at a time • Stops when an error occurs • Allows errors to be corrected in real time // errors can be corrected and translation continued from that point Compiler • Converts high level language code into low level code • Translates the whole program before attempting to run it • Creates an executable file/object code... • ... if there are no errors • Generates a report of all the errors 4 5(c) 1 mark per bullet point to max 2 • Formal / legal recognition of ownership // To protect her intellectual property rights • Formal / legal restrictions on the use of the program 2 Question Answer Marks 6 1 mark per bullet point to max 2 per utility program, max 4 in total File compression • Reduces the file size • ... by using algorithms to change the data • ... which can be either lossy or lossless Defragmenter • Finds files that are split across the disk • …and moves the blocks that make up each file to be contiguous • Collates free space 4

9608/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2021 © UCLES 2021 Page 7 of 9 Question Answer Marks 7 1 mark per pair of rows (shaded and unshaded) A B C Working space X 0 0 0 1 0 0 1 1 0 1 0 1 0 1 1 1 1 0 0 1 1 0 1 1 1 1 0 0 1 1 1 0 4 Question Answer Marks 8(a) 1 mark per correct relationship 3 8(b) 1 mark per bullet point • ALTER TABLE and correct table name (CONTRACT) • DROP and the correct attribute name (RefConNumber) ALTER TABLE CONTRACT DROP RefConNumber; 2

9608/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2021 © UCLES 2021 Page 8 of 9 Question Answer Marks 8(c) 1 mark for the shaded rows and 1 mark for the unshaded rows Statement DML DDL ADD PRIMARY KEY  ALTER TABLE  SELECT FROM  INNER JOIN  CREATE DATABASE  2 8(d) 1 mark per bullet point to max 2 per validation method, max 4 in total • Presence check • …to make sure the phone number is entered // to make sure the field is not left empty • Length check • …to make sure there are a maximum of 14 characters 4 8(e) 1 mark for a correct answer An attribute (or set of attributes) that could be a primary key 1 8(f) 1 mark per bullet point to max 2 • An attribute that can be indexed... • …for faster searching • An attribute that is a candidate key... • …but is not the primary key 2

9608/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2021 © UCLES 2021 Page 9 of 9 Question Answer Marks 8(g) 1 mark per bullet point to max 5 • The disk has one or more platters … • … made of aluminium/glass • The platters are coated with ferrous oxide which is capable of being magnetised • The platters/disks are mounted on a central spindle. • The disks are rotated at high-speed • Each surface of the disk has a read-write head mounted on an arm positioned just above the surface • Electronic circuits control the movement of the arm and hence the heads • The surface of the platter/disk is divided into concentric tracks and sectors • The data is encoded as a magnetic pattern for each block • When writing to disk, a variation in the current in the head produces a variation in magnetic field on the disk • When reading from disk, a variation in magnetic field produces a variation in current through the head 5 Question Answer Marks 9 1 mark per correct description Register transfer notation Description MAR ←[PC] The data stored in the Program Counter is passed to the Memory Address Register PC ←[PC] + 1 The Program Counter is incremented MDR ←[[MAR]] The data in the address pointed to by the Memory Address Register is passed to the Memory Data Register 3 Question Answer Marks 10(a) 1 mark for the correct answer 256 1 10(b) 1 mark for each correct answer Smallest: −128 Largest: +127 2