2022 BVSS 4E Computing Prelim P1 - Marking Scheme

1 Marking Scheme Q1 1 mark for each correct line. Maximum 4 lines. Description Spreadsheet Function FLOOR.MATH() Returns the integer portion of a division. HLOOKUP() Returns the remainder after a number is divided by a divisor. MOD() Rounds a number down to the nearest integer. OR() Looks for a value in the top row of a table or array of values and returns the value in the same column from a row specified. QUOTIENT() [4m] Q2 2(a) 35 employee names of string data types and 35 employee reporting times of date data type [1m] Note: Accept if the student specifies some valid range or dd-mm-yyyy or time. 2(b) Names of employees who are late for more than 3 times in the month and their average number of minutes late, rounded to appropriate accuracy. [1m] 2(c) List [1m] Any one of the following. Maximum 1 mark. ● A list of items can be indexed. In this case, the list can be used to store the 35 records. ● A repetition / loop can be used to process the list of 35 records and this makes the program code more concise.

2 Q3 3(a)(i) Any 1 from the following. Maximum 1 mark. ● Shared resources: A network allows a group of computers to make use of shared resources such as printers or files. ● Shared Internet access: Depending on the network’s configuration, every user who logs on to the network may have access to the Internet. ● Shared software: Software can be stored on the central server of a network and deployed to other computers over a network. ● Shared storage: Data files can be stored on a central server for ease of access and backup purposes. ● Communication: Computers in the same network are often able to share instant messages and emails for communication. 3(a)(ii) Any 1 from the following. Maximum 1 mark. ● Initial costs: Installing a network could be costly due to the high setup and equipment costs. ● Maintenance costs: There are also subsequent costs associated with administering and maintaining the network. ● Security risks: As files are shared through a network, there is the risk of virus or worm attacks spreading throughout the network even with just one infected computer. ● Risk of data loss: Data may become lost due to hardware failures or errors. Using a network means regular data backups are needed. ● Server outage: If the server fails, the network will not be able to function, thus affecting work processes.

3 3(b) 1 mark for identified network device and 1 mark for the description. Maximum 2 marks Network Device Description Network interface controller (NIC) NIC provides the hardware interface to enable the transfer of data between a device and a network. Network hub A device that transmits the received packets to all connected devices on the same network. Network switch A device that constructs a single network by connecting multiple similar networks together and it uses MAC addresses to keep track of the devices connected. Router A device that forwards packets between connected devices on separate networks by using the internet protocols where devices are identified by their IP addresses. Modem A device that is responsible for modulation and demodulation where modulation is to convert digital data into a form suitable for transmission while demodulation is the reverse process. Wireless Access Point Network hardware that provides a connection between wireless devices up to 100 metres away and can connect to wired networks. Network bridge A device that constructs a single network by connecting two similar networks together.

4 Q4 4(a) Description of privacy and security threats Term The interception of requests sent from a computer to a legitimate website and redirection to a fake website to steal personal data or credit card details. Pharming [1m] [1m] A small file used by websites to store personal information on a user’s web browser. Cookie The mass distribution of unwanted messages or advertising to email addresses. Spamming [1m] 4(b) Description: Type of authentication that uses evidence from both something the user knows and something the user owns. [1m] Example: To access his or her bank account online, the user has to confirm his or her identity by providing a secret password / personal identification number (PIN), followed by a one-time password (OTP) generated from the security token / a mobile phone that the user owns. [1m]

5 Q5 5(a) 1 mark for each correct Type of Storage Media. Description Type of Storage Media Data is stored as very small pits or indentations that can be read or written by a laser. Optical Data is stored in electronic circuits called “flash memory” that have no moving parts. Solid-state Data is stored on a material that can be read or written by a head. Magnetic 5(b) 372 x 1000 = 372000 bytes [1m] 5(b) 5600 / 1000 = 5.6 GB [1m] Q6 6(a) (i) Media Access Control [1m] (ii) Manufacturer identity number or Manufacturer Code [1m] (iii) Device serial number or Product serial number [1m] (iv) Any one of the following. Maximum 1 mark. ● To enable all devices to be uniquely identified. ● To identify a particular network interface controller. 6(b) #0000FF [1m] 6(c) The website is encrypted as its address starts with https:// . [1m]

6 Q7 1 mark for correct answer and 1 mark for showing relevant working. 7(a) 1010 (binary) = 10 (denary) = A (hexadecimal) 0011 (binary) = 3 (denary) = 3 (hexadecimal) [1m] 10100011 (binary) = A3 (hexadecimal) [1m] 7(b) C (hexadecimal) = 12 (denary) = 1100 (binary) 5 (hexadecimal) = 5 (denary) = 0101 (binary) [1m] C5 (hexadecimal) = 11000101 (binary) [1m] 7(c) 217 / 16 is 13 remainder 9 13 / 16 is 0 remainder 13 (which is D is hexadecimal) [1m] 217 = D9 (hexadecimal) [1m] 7(d) The position of a digit in a binary number determines its place value, which is represented by 2N. The place value starts from 20 for the rightmost digit, with the power (N) increasing by 1 for each subsequent digit on the left. [1m] Hence, 11100001 (binary) = 27 + 26 + 25 + 20 (or = 128 + 64 + 32 + 1) = 225 (denary) [1m]

7 Q8 8(a) WHILE mark < 0 or mark > 25 [1m] OUTPUT "Invalid input! Enter marks between 0 and 25 inclusive: " INPUT mark [1m] ENDWHILE [The 1m is awarded for both Error message and INPUT statement in the loop.] 8(b) Test case condition Test data for marks Normal Example: 1, 15 Error Example: -2, 27 Boundary Example: -1, 0, 25, 26 [3m] Q9 9(a) Maximum 5 marks. i count1 count2 num OUTPUT 0 0 0 1 12.4 1 1 8 2 2 25 3 2 17.8 4 3 6 3 2 [1m] [1m] [1m] [1m] [1m] 9(b) The algorithm is to count the number of integers and floating point numbers from an input of 5 numbers. [1m]

8 Q10 10(a) Maximum 4 marks. Z Correct use of NOT gate [1m] Correct use of NAND gate [1m] Correct use of AND gate [1m] Correct use of OR gate [1m] 10(b) 1 mark for each correct 2 rows. Maximum 4 marks. Z = (P AND NOT Q) OR (P NAND R) P Q R Working Space Z= B OR C A= NOT Q B= P AND A C = P NAND R 0 0 0 1 0 1 1 0 0 1 1 0 1 1 0 1 0 0 0 1 1 0 1 1 0 0 1 1 1 0 0 1 1 1 1 1 0 1 1 1 0 1 1 1 0 0 0 1 1 1 1 1 0 0 0 0 P Q C R L Z

9 Q11 11(a) Any one: removed, new_name, name, i [1m] Note: The variable stated must be same case as given in the question. 11(b) One mark for each error identified. One mark for suggested correction. Error 1 : 04 FOR i = 0 to len(name) Correction : FOR i = 0 to len(name)-1 [1m] [1m] Error 2 : 05 IF name[i]== " " and name[i].isdigit()== True Correction : IF name[i]== " " or name[i].isdigit()== True [1m]