Cambridge A Level Computer Science 9618 — 2022 May/June Paper 1 · Variant 3

This document has 16 pages. Any blank pages are indicated. [Turn over Cambridge International AS & A Level * 4 1 5 8 9 4 4 3 1 5 * DC (PQ/CGW) 301925/5 © UCLES 2022 COMPUTER SCIENCE 9618/13 Paper 1 Theory Fundamentals May/June 2022 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 9618/13/M/J/22 © UCLES 2022 1 Text and numbers are examples of data stored in a computer. (a) A character set is used to represent characters in a computer. (i) Describe what is meant by a character set. … … … … … … [2] (ii) Identify two character sets and state one difference between them. Character set 1 … Character set 2 … Difference … … [3] (iii) Describe how lossless compression can be used to reduce the file size of a text file. … … … … … … [2] (iv) Explain why lossy compression should not be used on a text file. … … … … … … [2]

3 9618/13/M/J/22 © UCLES 2022 [Turn over (b) A computer can represent numerical data in different forms. Complete the table by writing the answer to each statement. Statement Answer The hexadecimal value 11 represented in denary The smallest denary number that can be represented by an unsigned 8-bit binary integer The denary number 87 represented in Binary Coded Decimal (BCD) The denary number 240 represented in hexadecimal The denary number –20 represented in 8-bit two’s complement binary [5] Working space … … … … … … … … … … … … … … … …

4 9618/13/M/J/22 © UCLES 2022 2 (a) The Fetch-Execute (F-E) cycle is represented in register transfer notation. Describe each of the given steps. Step Description PC [PC] + 1 … … … MDR [[MAR]] … … … MAR [PC] … … … [3] (b) Explain how interrupts are handled during the F-E cycle. … … … … … … … … … … … … … [5]

5 9618/13/M/J/22 © UCLES 2022 [Turn over BLANK PAGE

6 9618/13/M/J/22 © UCLES 2022 3 (a) The table shows part of the instruction set for a processor. The processor has one general purpose register, the Accumulator (ACC). Instruction Explanation Opcode Operand LDM #n Immediate addressing. Load the number n to ACC LDD <address> Direct addressing. Load the contents of the location at the given address to ACC LDI <address> Indirect addressing. The address to be used is at the given address. Load the contents of this second address to ACC <address> can be an absolute or symbolic address # denotes a denary number, e.g. #123 The current contents of main memory are: Address 100 101 101 67 102 104 103 100 104 68 Complete the table by writing the value stored in the accumulator after the execution of each instruction. Instruction Accumulator LDM #103 LDD 102 LDI 103 [3]

7 9618/13/M/J/22 © UCLES 2022 [Turn over (b) The instructions in part (a) are examples of the data movement group. Describe two other instruction groups. 1 … … … … 2 … … … … [4]

8 9618/13/M/J/22 © UCLES 2022 (c) The table shows part of the instruction set for a processor. The processor has one general purpose register, the Accumulator (ACC). Instruction Explanation Opcode Operand AND Bn Bitwise AND operation of the contents of ACC with the operand XOR Bn Bitwise XOR operation of the contents of ACC with the operand OR Bn Bitwise OR operation of the contents of ACC with the operand B denotes a binary number, e.g. B01001010 The binary value 00111101 is stored in the memory address 200. Each instruction in the diagram is performed on the data in memory address 200. Draw one line from each instruction to its correct result. Instruction Result XOR B11110000 OR B01010101 AND B11111111 01111101 00111101 11111111 11000010 11001101 [3]

9 9618/13/M/J/22 © UCLES 2022 [Turn over 4 A computer has system software including an operating system. (a) Describe the key management tasks of an operating system. … … … … … … … … … … … [4] (b) Utility software is a type of system software. (i) Describe the purpose of back-up software and defragmentation software. Back-up software … … … … Defragmentation software … … … … [4] (ii) Give one other example of utility software. … [1]

10 9618/13/M/J/22 © UCLES 2022 5 A company wants to store data about its employees in a computer system. The owner of the company wants to ensure the security and integrity of the data. (a) (i) State why data needs to be kept secure. … … [1] (ii) One way the data stored in a computer can be kept secure is by using back-up software. Give two other ways the data stored in a computer can be kept secure. 1 … … 2 … … [2] (b) The data about the employees is currently stored on paper. The data needs to be transferred into the computer system. Data validation and verification are used to help maintain the integrity of the data. (i) Identify and describe one method of data verification that can be used when transferring the data from paper to the computer. Method … Description … … … [2] (ii) The company needs to transfer the date of birth of each employee into the computer system. Give one example of how each of the following data validation rules can be used to validate the date of birth when it is entered into the system. Range check … … Presence check … … Length check … … [3]

11 9618/13/M/J/22 © UCLES 2022 [Turn over (iii) Explain why the data in the system may not be correct even after validating and verifying the data. … … … … … … [2]

12 9618/13/M/J/22 © UCLES 2022 6 A relational database, TECHNOLOGY, stores data about the staff in a company and the computer devices used by the staff. The database has the following tables: STAFF(StaffID, FirstName, LastName, DateOfBirth, JobTitle) DEVICE(DeviceID, Type, DatePurchased, StaffID) (a) Describe the relationship between the two tables. Refer to the primary and foreign keys in your answer. … … … … … … … … [4] (b) The database uses a Data Definition Language (DDL) and Data Manipulation Language (DML). (i) Complete the SQL script to return the number of devices stored in the database for the staff member with the first name ‘Ali’ and last name ‘Khan’. SELECT … (STAFF.StaffID) FROM … INNER JOIN DEVICE … STAFF.StaffID = DEVICE.StaffID WHERE STAFF.FirstName = 'Ali' … STAFF.LastName = 'Khan'; [4]

13 9618/13/M/J/22 © UCLES 2022 [Turn over (ii) The table DEVICE needs a new attribute to store whether the device has been returned by the staff member, or not. Write a Structured Query Language (SQL) script to insert the new attribute into the table DEVICE. … … … … [2] (c) The database is in Third Normal Form (3NF). Complete the table by describing the three normal forms. Normal Form Description First Normal Form (1NF) … … … … Second Normal Form (2NF) … … … … Third Normal Form (3NF) … … … … [3]

14 9618/13/M/J/22 © UCLES 2022 7 (a) Write the logic expression for the following logic circuit. A B X C … … [3] (b) Complete the truth table for the following logic expression: X = (A NAND B) OR (A AND NOT 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 [2]

15 9618/13/M/J/22 © UCLES 2022 8 A company uses cloud computing. (a) Define cloud computing. … … [1] (b) State what is meant by a public cloud and a private cloud. Public cloud … … Private cloud … … [2] (c) Give two benefits and one drawback of using cloud computing. Benefit 1 … … Benefit 2 … … Drawback … … [3]

16 9618/13/M/J/22 © UCLES 2022 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 Cambridge Assessment. Cambridge Assessment is the brand name of the University of Cambridge Local Examinations Syndicate (UCLES), which is a department of the University of Cambridge. BLANK PAGE

This document consists of 10 printed pages. © UCLES 2022 [Turn over Cambridge International AS & A Level COMPUTER SCIENCE 9618/13 Paper 13 Theory Fundamentals May/June 2022 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 2022 series for most Cambridge IGCSE, Cambridge International A and AS Level and Cambridge Pre-U components, and some Cambridge O Level components.

9618/13 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2022 © UCLES 2022 Page 2 of 10 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.

9618/13 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2022 © UCLES 2022 Page 3 of 10 Question Answer Marks 1(a)(i) 1 mark per point to max 2  All of the characters/symbols that the computer can use/represent  Each character has a unique number/binary number/hexadecimal number 2 1(a)(ii) 1 mark for each character set to max 2, 1 mark for difference  ASCII  Extended ASCII  UNICODE  ASCII has 7 bits whereas UNICODE has 16 bits  Extended ASCII has 8 bits whereas UNICODE has 16 bits  ASCII has 7 bits whereas extended ASCII has 8 bits  Unicode can represent more characters than ASCII/Extended// by example  Extended ASCII can represent more characters than ASCII 3 1(a)(iii) 1 mark per point to max 2  Can use run-length encoding  Identifies groups of repeated characters ...  ... replaces them with a one copy of the character and the number of times it occurs 2 1(a)(iv) 1 mark per point to max 2  None of the original data can be lost / deleted  The (text) file would be corrupted // the (text) file cannot be opened 2 1(b) 1 mark for each correct value Statement Answer The hexadecimal value 11 represented in denary 17 The smallest denary number that be represented by an unsigned 8-bit binary integer 0 The denary number 87 represented in Binary Coded Decimal (BCD) 1000 0111 The denary number 240 represented in hexadecimal F0 The denary number –20 represented in 8-bit two’s complement binary 1110 1100 5

9618/13 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2022 © UCLES 2022 Page 4 of 10 Question Answer Marks 2(a) 1 mark for each correct description Step Description PC  [PC] + 1 Address in PC is incremented MDR  [[MAR]] The data in the address held in the MAR is copied to the MDR MAR  [PC] The contents of the PC are copied to the MAR 3 2(b) 1 mark per point to max 5  Check for interrupt at start/end of an F-E cycle  Priority is checked  If lower priority than current process continue with F-E cycle  If higher priority than current process …  … state of current process is / registers are stored on stack  Location/type of interrupt identified  Appropriate ISR is called to handle the interrupt  When ISR finished, check for further interrupts (of higher priority) / return to step 1  Otherwise load data from stack and continue with next F-E cycle (of process) 5 Question Answer Marks 3(a) 1 mark for each correct value Instruction Accumulator LDM #103 103 LDD 102 104 LDI 103 101 3

9618/13 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2022 © UCLES 2022 Page 5 of 10 Question Answer Marks 3(b) 1 mark for group name, 1 mark for appropriate description e.g.  Input and output of data  Takes an input from the user // outputs the character of the binary number  Arithmetic operations  Perform addition and subtraction  Unconditional and conditional instructions  Move to another instruction (identified by a label)  Compare instructions  Compare the result to another value 4 3(c) 1 mark for each correct line Instruction Result 01111101 XOR 11110000 00111101 OR 01010101 11111111 AND 11111111 11000010 11001101 3

9618/13 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2022 © UCLES 2022 Page 6 of 10 Question Answer Marks 4(a) 1 mark for identifying task, max 2 for each description Max 2 for only identifying tasks without descriptions e.g.  Memory management  Controls the movement of data between RAM, processor, VM etc  allocates memory to processes  File management  Creates files/folders  Renames file/folders  Security management  Creates accounts/passwords  Provide /upgrade firewall / anti-malware  Hardware management  Receives data from input devices ///sends data to output device  Use of device drivers  Process management  Decides which process to run next  supports multitasking 4 4(b)(i) 1 mark per point to max 2 for each Back-up  To make a copy of data at regular intervals  So that if it is lost/corrupted it can be retrieved Defragmentation  Make individual files occupy contiguous blocks // move free space together  Improve disk access times // Data/files can be loaded faster 4 4(b)(ii) 1 mark from e.g.  Compression software  (Hard) disk formatter  Virus checker  Disk analysis software  Disk repair software 1

9618/13 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2022 © UCLES 2022 Page 7 of 10 Question Answer Marks 5(a)(i) 1 mark from  To stop the data being lost / corrupted / amended  To make sure it can be recovered  To prevent unauthorised access 1 5(a)(ii) 1 mark each e.g.  Install / run a firewall  Up to date Anti-virus / anti-malware  (Username and) (strong) password  Encryption  Access rights 2 5(b)(i) 1 mark each  Visual check  Manually compare the data entered with the original (document)  Double entry  Enter the data twice and the system compares them to see if they are the same 2 5(b)(ii) 1 mark each e.g. Range check:  Make sure it is after and before a specific date // e.g. between 1900 and today's date // check month is between 1 and 12 // check day is between 1 and month end Presence check:  Make sure the date of birth has been entered Length check:  Make sure there are at least 1 for day, 1 for month, 2/4 for year // must be 8 characters 3 5(b(iii) 1 mark per bullet point to max 2  Validation checks data is reasonable/within bounds it does not check that accurate data has been entered  Verification checks if the data matches the data given it does not check if the original data is accurate 2

9618/13 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2022 © UCLES 2022 Page 8 of 10 Question Answer Marks 6(a) 1 mark per point  Primary key StaffID in STAFF…  …links to foreign key StaffID in DEVICE  One staff member can have many devices  Each device can only be with one member of staff 4 6(b)(i) 1 mark for each correctly completed statement SELECT COUNT(STAFF.StaffID) FROM STAFF INNER JOIN DEVICE ON STAFF.StaffId = DEVICE.StaffID WHERE STAFF.FirstName = "Ali" AND STAFF.LastName = "Khan"; 4 6(b)(ii) 1 mark per bullet point  ALTER TABLE DEVICE  ADD appropriate field name, appropriate data type e.g. ALTER TABLE DEVICE ADD Returned Boolean; 2 6(c) Normal Form Description First Normal Form (1NF) No repeating groups or repeating attributes Second Normal Form (2NF) All attributes must be fully dependant on the (composite) primary key // No partial dependencies Third Normal Form (3NF) All attributes must be fully dependent on the primary key and no other attributes // no non-key dependencies // no transitive dependencies 1 mark for each correct description 3

9618/13 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2022 © UCLES 2022 Page 9 of 10 Question Answer Marks 7(a) 1 mark for each section  A AND B  NOT C AND B // B AND NOT C  XOR (with remainder correct and bracketed and nothing extra) X = (A AND B) XOR (NOT C AND B) 3 7(b) 1 mark for first 4 rows, 1 mark for second 4 rows (shaded) 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 1 1 1 1 0 2 Question Answer Marks 8(a) Accessing a service/files/software on a remote server 1 8(b) 1 mark each from: Public e.g.  Computing services offered by 3rd party provider over the public Internet  Public is open/available to anyone with the appropriate equipment/software/credentials Private e.g.  Computing services offered either over the Internet or a private internal network  Only available to select users not the general public  Private is a dedicated/bespoke system only accessible for/from the organisation 2

9618/13 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2022 © UCLES 2022 Page 10 of 10 Question Answer Marks 8(c) 1 mark for each benefit to max 2 e.g.  Can be accessed anywhere with Internet access  Do not need to install security // security might be better  Do not need to perform backups  Do not need to buy specific software/hardware  Can easily share documents  Can have multiple people working on the same document 1 mark for drawback e.g.  You cannot access it if no internet access  Reliant on someone else to backup  Reliant on someone else for security // can have poorer security  Cannot access if server goes down 3