BVSS Prelim P1 MS

2024 Sec 4 Express Computing P1 Marking Scheme Qn Answers Marks 1 (a) 203 1 (b) 1 mark for each point • Divide 298 repeatedly by 16 and record the respective remainder, until the quotient is 0 • For remainder 0 – 9, the hexadecimal digit is the same. For remainder 10 – 15, the hexadecimal digit is A to F respectively. The hexadecimal number is the remainder read from bottom up • 298 = 12A Alternate solution: • Convert to binary - Divide 298 repeatedly by 2 and record the respective remainder until the quotient is 0 - The binary number is the remainder read from bottom up • From the rightmost, group 4 bits into 1 hexadecimal digit. Find the denary equivalent of each group of 4 bits. For 0 – 9, the hexadecimal digit is the same. For 10 – 15, the hexadecimal digit is A to F respectively. • 298 = 1 0010 1010 = 12A 3 (c) • Manufacturer's identity number • Device's serial number 1 1 (d) • 3116 = 0011 0001 The last 8 bits of the device in (c) is not 0111 0001. • Hence, the device is (c) is not the unauthorised device Alternative solution: • 0111 0001 = 7116 The hexadecimal is not 31. • Hence, the device in (c) is not the unauthorised device 1 1 2 MID SMALL VLOOKUP SUMIF COUNTBLANK 1 1 1 1 1

3 4 4 (a) Trojan horse [any one] • a computer program that pretends to be a harmless or useful application • once a trojan horse is run, it does something harmful such as giving intruders unauthorised access to the computer Worm • a computer program that runs automatically and attempts to spread by sending copies of itself to other computers Pharming • the interception of requests sent to a legitimate website and redirection to a fake website to steal personal data 1 1 1

(b) Positive [any one] • better videos, simulations and collaboration tools makes lessons more engaging • sharing of information on the Internet makes education accessible to all • enables improved communication between learners and teachers Negative [any one] • leads to learners' shorter attention span • heavy investment in materials and infrastructure • need to retrain and pick up new skills 1 1 (c) The crime of copying, distributing and/or using proprietary software in a manner that is not permitted by its licence 1 5 (a) Valid stores a Boolean that indicates if Value is a valid binary or not. If Value contains only '0' and/or '1', Valid is True. Otherwise, Valid is False [must be in the context of the question] 1 1 (b) (i) Main program Check() Success() Data Result Output Valid Count Value returned Total Value returned 13111 TRUE 0 FALSE FALSE 1 FALSE Error 1 mark for main program 1 mark for Check() 2

(b) (ii) Main program Check() Success() Data Result Output Valid Count Value returned Total Value returned 10011 TRUE 0 1 2 3 TRUE 4 TRUE 0 1 2 FALSE 3 FALSE ERROR 1 mark for main program 1 mark for Check() 1 mark for Success() 3 (iii) Function Success() is used to count the number of '1's in Value and/or check if there are even or odd number of '1's. If it is even, the function returns True. If it is odd, the function returns False. Parity check (even parity system) 1 1 1

6 (a) Compiler 1 (b) [any two] • Interpreter translates and run one statement of the source code at a time / translation occurs while the program is running / translation stops when syntax error is detected • The interpreter program is needed every time the program is run • Changes to the source code takes effect immediately • Interpreters usually offer an interactive mode which facilitates learning 2 (c) [any two] • Compiler translates the entire source code into machine code • The compiler program is not needed to run the program • Any changes to the source code requires recompilation before the changes takes effect • Compilers usually do not offer an interactive mode 2 7 (a) [any two] A LAN is a network of computing devices connected within a small geographical area (e.g. within a building) while a WAN is a network of devices connected across geographical locations Data transfer is faster in LAN compared to a WAN A WAN uses more expensive and high-speed technology than a LAN 1 1 (b) [any 2] Network hub A device that transmits received packets to all connected devices Network interface controller An internal component that provides the hardware interface to enable the transfer of data between a device and a network Network switch A switch connects multiple LANs that use the same protocol so that the combined network can cover a larger physical area. A switch uses MAC addresses to keep track of the devices that are connected to it. Router A device that forwards packets between separate networks Modem (spelling MUST be correct) A device that converts digital data into a form suitable for transmission and converts transmitted signals into digital data. 4

(c) The server is a computer that shares resources such as the children's personal data, and responds to requests from devices used by staff and teachers. It also manages the logins of the staff and teachers in the different classrooms. When a teacher uses a computer to enter or retrieve children's information, the computer initiates a connection to the server requesting for information from the server and /or to save the information into the centralized database. 1(s) 1(c) 8 (a) Decomposition is a technique of breaking down a complex problem into smaller and more manageable parts. The solutions to these parts are then combined to solve the original problem. 2 (b) [any two] Member ID (e.g. T1234567A) • Length check: length of MemberID is 9 characters long • Format check: MemberID is made up of letters in the first and last position, filled with digits in between) Class (e.g. 1A) • Length check: length of class is 2 characters long • Format check: first character is a digit followed by a letter Book title / author • Presence check: the book title is entered Fine paid • Range check: the amount paid is a numerical value greater than 0 2 (c) [any two] • Receipt showing the books the students borrowed • The result of a search based on title, author, genre, etc • The number of books borrowed by a particular class/level • List of overdue loans 2 (d) [any two] • Students can borrow only books that are available, customers can only order items that are in stock • Availability/copies of books are updated upon a loan/return, the stock is updated when customers order items • Search for books; search for items [MUST describe the aspect in BOTH system] 2

9 (a) Line 13 • OUTPUT "Credit card no: ", Remove(CardNum) Line 4 • While Counter < LEN(Num) • While Counter <= LEN(Num)-1 Line 6 • NewNum += Num[Counter] Line 10 • RETURN NewNum 1 1 1 1 (b) Run-time error • An error that occurs while the program is running, usually causing the program to hang or crash Syntax error • An error that is detected by the translator due to incorrect source code that does not follow the rules of the language 1 1 1 1 (c) Test and refine code 1 (d) Test case condition Test data Normal 1111-2222-3333 Error 1111 2222 3333 1234 aaaa-bbbb-cccc 1 mark for each test data; must be for different types of error • 14 characters – no '-' in the correct position, not digits in the correct positions • Not 14 characters • Did not accept empty string (since there are other possible clearer responses) 4

10 (a)(i) A = (L AND S) OR (L and NOT V) Or A = L AND (S OR NOT V) 1 (ii)